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0
math_hard
b360141a-c7fb-52a8-b9ce-a46404d1ece8
"If a whole number $n$ is not prime, then the whole number $n-2$ is not prime." A value of $n$ which shows this statement to be false is $\textbf{(A)}\ 9 \qquad \textbf{(B)}\ 12 \qquad \textbf{(C)}\ 13 \qquad \textbf{(D)}\ 16 \qquad \textbf{(E)}\ 23$
A. 9.0
null
null
di-zhang-fdu/AOPS
false
true
1
math_hard
4c72d3f3-e08b-5ae6-8354-fa6affe00057
$(1+11+21+31+41)+(9+19+29+39+49)=$ $\text{(A)}\ 150 \qquad \text{(B)}\ 199 \qquad \text{(C)}\ 200 \qquad \text{(D)}\ 249 \qquad \text{(E)}\ 250$
E. 250.0
null
null
di-zhang-fdu/AOPS
false
true
2
math_hard
aac23d98-b8f9-5756-9c7f-8474bd409548
$(1901+1902+1903+\cdots + 1993) - (101+102+103+\cdots + 193) =$ $\text{(A)}\ 167,400 \qquad \text{(B)}\ 172,050 \qquad \text{(C)}\ 181,071 \qquad \text{(D)}\ 199,300 \qquad \text{(E)}\ 362,142$
A. 167400.0
null
null
di-zhang-fdu/AOPS
false
true
3
math_hard
fde68796-6be6-5bb8-b3d2-5c27ce275159
$(2\times 3\times 4)\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}\right) =$ $\text{(A)}\ 1 \qquad \text{(B)}\ 3 \qquad \text{(C)}\ 9 \qquad \text{(D)}\ 24 \qquad \text{(E)}\ 26$
E. 26.0
null
null
di-zhang-fdu/AOPS
false
true
4
math_hard
44ac58cb-9e34-574d-a966-529ceb0d719c
$-15+9\times (6\div 3) =$ $\text{(A)}\ -48 \qquad \text{(B)}\ -12 \qquad \text{(C)}\ -3 \qquad \text{(D)}\ 3 \qquad \text{(E)}\ 12$
D. 3.0
null
null
di-zhang-fdu/AOPS
false
true
5
math_hard
3aaf1e83-3107-5463-9ca7-a8619729111e
$.4+.02+.006=$ $\text{(A)}\ .012 \qquad \text{(B)}\ .066 \qquad \text{(C)}\ .12 \qquad \text{(D)}\ .24 \qquad \text{(E)} .426$
E. 0.426
null
null
di-zhang-fdu/AOPS
false
true
6
math_hard
b3c9f161-620b-54f1-914f-a2a1aecc3fe3
$1,000,000,000,000-777,777,777,777=$ $\text{(A)}\ 222,222,222,222 \qquad \text{(B)}\ 222,222,222,223 \qquad \text{(C)}\ 233,333,333,333 \qquad \\ \text{(D)}\ 322,222,222,223 \qquad \text{(E)}\ 333,333,333,333$
B. 222222222223.0
null
null
di-zhang-fdu/AOPS
false
true
7
math_hard
ec70ad93-2f44-59a1-9d0b-8adb6f2f6858
$1-2-3+4+5-6-7+8+9-10-11+\cdots + 1992+1993-1994-1995+1996=$ $\text{(A)}\ -998 \qquad \text{(B)}\ -1 \qquad \text{(C)}\ 0 \qquad \text{(D)}\ 1 \qquad \text{(E)}\ 998$
C. 0.0
null
null
di-zhang-fdu/AOPS
false
true
8
math_hard
543ee2f1-8015-51fb-af4e-27d624c96fdc
$10\times10\times10$ grid of points consists of all points in space of the form $(i,j,k)$ , where $i$ $j$ , and $k$ are integers between $1$ and $10$ , inclusive. Find the number of different lines that contain exactly $8$ of these points.
168.0
null
null
di-zhang-fdu/AOPS
false
true
9
math_hard
a765c9a0-aada-5ff4-ab82-eb32c5195f38
$150\times 324\times 375$ rectangular solid is made by gluing together $1\times 1\times 1$ cubes. An internal diagonal of this solid passes through the interiors of how many of the $1\times 1\times 1$ cubes
768.0
null
null
di-zhang-fdu/AOPS
false
true
10
math_hard
fec37a7c-9192-562f-b40e-bf56ea321f99
$1990-1980+1970-1960+\cdots -20+10 =$ $\text{(A)}\ -990 \qquad \text{(B)}\ -10 \qquad \text{(C)}\ 990 \qquad \text{(D)}\ 1000 \qquad \text{(E)}\ 1990$
D. 1000.0
null
null
di-zhang-fdu/AOPS
false
true
11
math_hard
761ee3ff-067d-5ce9-a9c0-a1ad34c7c522
$2 \times 3$ rectangle and a $3 \times 4$ rectangle are contained within a square without overlapping at any point, and the sides of the square are parallel to the sides of the two given rectangles. What is the smallest possible area of the square? $\textbf{(A) } 16\qquad \textbf{(B) } 25\qquad \textbf{(C) } 36\qquad \...
B. 25.0
null
null
di-zhang-fdu/AOPS
false
true
12
math_hard
19bf7f44-e302-5644-98c5-7b0d0d3a7685
$2$ by $2$ square is divided into four $1$ by $1$ squares. Each of the small squares is to be painted either green or red. In how many different ways can the painting be accomplished so that no green square shares its top or right side with any red square? There may be as few as zero or as many as four small green s...
B. 6.0
null
null
di-zhang-fdu/AOPS
false
true
13
math_hard
1912a4d4-c5bc-5b6a-b8c5-7db892189bd2
$2(81+83+85+87+89+91+93+95+97+99)=$ $\text{(A)}\ 1600 \qquad \text{(B)}\ 1650 \qquad \text{(C)}\ 1700 \qquad \text{(D)}\ 1750 \qquad \text{(E)}\ 1800$
E. 1800.0
null
null
di-zhang-fdu/AOPS
false
true
14
math_hard
7930878b-ac63-509f-a5ce-1a59664fc2cd
$25$ foot ladder is placed against a vertical wall of a building. The foot of the ladder is $7$ feet from the base of the building. If the top of the ladder slips $4$ feet, then the foot of the ladder will slide: $\textbf{(A)}\ 9\text{ ft} \qquad \textbf{(B)}\ 15\text{ ft} \qquad \textbf{(C)}\ 5\text{ ft} \qquad \textb...
D. 8.0
null
null
di-zhang-fdu/AOPS
false
true
15
math_hard
df281d8c-a6bb-51a2-8987-3d79b5d7a03e
$2\left(1-\dfrac{1}{2}\right) + 3\left(1-\dfrac{1}{3}\right) + 4\left(1-\dfrac{1}{4}\right) + \cdots + 10\left(1-\dfrac{1}{10}\right)=$ $\text{(A)}\ 45 \qquad \text{(B)}\ 49 \qquad \text{(C)}\ 50 \qquad \text{(D)}\ 54 \qquad \text{(E)}\ 55$
A. 45.0
null
null
di-zhang-fdu/AOPS
false
true
16
math_hard
d8c21f4f-1261-5328-9c80-fb38b0033d1c
$3 \times 7$ rectangle is covered without overlap by 3 shapes of tiles: $2 \times 2$ $1\times4$ , and $1\times1$ , shown below. What is the minimum possible number of $1\times1$ tiles used? $\textbf{(A) } 1\qquad\textbf{(B)} 2\qquad\textbf{(C) } 3\qquad\textbf{(D) } 4\qquad\textbf{(E) } 5$
E. 5.0
null
null
di-zhang-fdu/AOPS
false
true
17
math_hard
d26732be-de99-5fef-8b97-f8e75dc16abd
$4(299)+3(299)+2(299)+298=$ $\text{(A)}\ 2889 \qquad \text{(B)}\ 2989 \qquad \text{(C)}\ 2991 \qquad \text{(D)}\ 2999 \qquad \text{(E)}\ 3009$
B. 2989.0
null
null
di-zhang-fdu/AOPS
false
true
18
math_hard
a9401ee2-e8d3-554c-832a-3efd306ae307
$4\times 4$ block of calendar dates is shown. First, the order of the numbers in the second and the fourth rows are reversed. Then, the numbers on each diagonal are added. What will be the positive difference between the two diagonal sums? $\begin{tabular}[t]{|c|c|c|c|} \multicolumn{4}{c}{}\\\hline 1&2&3&4\\\hline 8&9&...
B. 4.0
null
null
di-zhang-fdu/AOPS
false
true
19
math_hard
26dfcc62-8b04-5dbb-8a62-566d695a858b
$4\times 4\times 4$ cubical box contains 64 identical small cubes that exactly fill the box. How many of these small cubes touch a side or the bottom of the box? $\text{(A)}\ 48 \qquad \text{(B)}\ 52 \qquad \text{(C)}\ 60 \qquad \text{(D)}\ 64 \qquad \text{(E)}\ 80$
B. 52.0
null
null
di-zhang-fdu/AOPS
false
true
20
math_hard
42cafa46-543b-5006-97f6-18f2e8561872
$7\times 1$ board is completely covered by $m\times 1$ tiles without overlap; each tile may cover any number of consecutive squares, and each tile lies completely on the board. Each tile is either red, blue, or green. Let $N$ be the number of tilings of the $7\times 1$ board in which all three colors are used at least ...
106.0
null
null
di-zhang-fdu/AOPS
false
true
21
math_hard
00536928-e12e-58eb-8a45-31bb27c5f7a6
$90+91+92+93+94+95+96+97+98+99=$ $\text{(A)}\ 845 \qquad \text{(B)}\ 945 \qquad \text{(C)}\ 1005 \qquad \text{(D)}\ 1025 \qquad \text{(E)}\ 1045$
B. 945.0
null
null
di-zhang-fdu/AOPS
false
true
22
math_hard
e0bd114c-059c-53a3-8b21-6ced49528d16
$A$ $B$ $C$ are three piles of rocks. The mean weight of the rocks in $A$ is $40$ pounds, the mean weight of the rocks in $B$ is $50$ pounds, the mean weight of the rocks in the combined piles $A$ and $B$ is $43$ pounds, and the mean weight of the rocks in the combined piles $A$ and $C$ is $44$ pounds. What is the grea...
E. 59.0
null
null
di-zhang-fdu/AOPS
false
true
23
math_hard
8fe98533-0893-5393-97ce-5d88414f1e2a
$A$ and $B$ together can do a job in $2$ days; $B$ and $C$ can do it in four days; and $A$ and $C$ in $2\frac{2}{5}$ days. The number of days required for A to do the job alone is: $\textbf{(A)}\ 1 \qquad \textbf{(B)}\ 3 \qquad \textbf{(C)}\ 6 \qquad \textbf{(D)}\ 12 \qquad \textbf{(E)}\ 2.8$
B. 3.0
null
null
di-zhang-fdu/AOPS
false
true
24
math_hard
d42e5527-7ccd-5fad-8f8b-2cef1fc445ca
$ABCD$ is a rectangular sheet of paper that has been folded so that corner $B$ is matched with point $B'$ on edge $AD.$ The crease is $EF,$ where $E$ is on $AB$ and $F$ is on $CD.$ The dimensions $AE=8, BE=17,$ and $CF=3$ are given. The perimeter of rectangle $ABCD$ is $m/n,$ where $m$ and $n$ are relatively prime posi...
293.0
null
null
di-zhang-fdu/AOPS
false
true
25
math_hard
493d82ac-972f-50a8-b9a4-c47c2d9facdd
$ABCD$ is a square of side length $\sqrt{3} + 1$ . Point $P$ is on $\overline{AC}$ such that $AP = \sqrt{2}$ . The square region bounded by $ABCD$ is rotated $90^{\circ}$ counterclockwise with center $P$ , sweeping out a region whose area is $\frac{1}{c} (a \pi + b)$ , where $a$ $b$ , and $c$ are positive integers and ...
C. 19.0
null
null
di-zhang-fdu/AOPS
false
true
26
math_hard
4a1d7713-20cf-567e-ae14-c91105024f9c
$ABCDE$ is a regular pentagon. $AP, AQ$ and $AR$ are the perpendiculars dropped from $A$ onto $CD, CB$ extended and $DE$ extended, respectively. Let $O$ be the center of the pentagon. If $OP = 1$ , then $AO + AQ + AR$ equals [asy] defaultpen(fontsize(10pt)+linewidth(.8pt)); pair O=origin, A=2*dir(90), B=2*dir(18), C=2...
C. 4.0
null
null
di-zhang-fdu/AOPS
false
true
27
math_hard
8034824e-de13-518e-b7a8-cdecd800656b
$R$ varies directly as $S$ and inversely as $T$ . When $R = \frac{4}{3}$ and $T = \frac {9}{14}$ $S = \frac37$ . Find $S$ when $R = \sqrt {48}$ and $T = \sqrt {75}$ $\textbf{(A)}\ 28\qquad\textbf{(B)}\ 30\qquad\textbf{(C)}\ 40\qquad\textbf{(D)}\ 42\qquad\textbf{(E)}\ 60$
B. 30.0
null
null
di-zhang-fdu/AOPS
false
true
28
math_hard
7b468ae5-d0d5-55b5-bce2-16901da98ef7
$[x-(y-z)] - [(x-y) - z] =$ $\textbf{(A)}\ 2y \qquad \textbf{(B)}\ 2z \qquad \textbf{(C)}\ -2y \qquad \textbf{(D)}\ -2z \qquad \textbf{(E)}\ 0$
B. 2.0
null
null
di-zhang-fdu/AOPS
false
true
29
math_hard
e4d40c5b-afdb-5e80-a01b-a58cb4724451
$\angle 1 + \angle 2 = 180^\circ$ $\angle 3 = \angle 4$ Find $\angle 4.$ [asy] pair H,I,J,K,L; H = (0,0); I = 10*dir(70); J = I + 10*dir(290); K = J + 5*dir(110); L = J + 5*dir(0); draw(H--I--J--cycle); draw(K--L--J); draw(arc((0,0),dir(70),(1,0),CW)); label("$70^\circ$",dir(35),NE); draw(arc(I,I+dir(250),I+dir(290),CC...
D. 35.0
null
null
di-zhang-fdu/AOPS
false
true
30
math_hard
29d7f9a7-0b6b-5e86-a5e7-f0cf013a17ae
$\dfrac{10-9+8-7+6-5+4-3+2-1}{1-2+3-4+5-6+7-8+9}=$ $\text{(A)}\ -1 \qquad \text{(B)}\ 1 \qquad \text{(C)}\ 5 \qquad \text{(D)}\ 9 \qquad \text{(E)}\ 10$
B. 1.0
null
null
di-zhang-fdu/AOPS
false
true
31
math_hard
6a8c96a1-9374-56f0-9106-a45eb85e1690
$\dfrac{1}{10} + \dfrac{9}{100} + \dfrac{9}{1000} + \dfrac{7}{10000} =$ $\text{(A)}\ 0.0026 \qquad \text{(B)}\ 0.0197 \qquad \text{(C)}\ 0.1997 \qquad \text{(D)}\ 0.26 \qquad \text{(E)}\ 1.997$
C. 0.1997
null
null
di-zhang-fdu/AOPS
false
true
32
math_hard
64be6f0c-e010-57f4-a174-b7448e7b9fe9
$\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}+\dfrac{55}{10}=$ $\text{(A)}\ 4\dfrac{1}{2} \qquad \text{(B)}\ 6.4 \qquad \text{(C)}\ 9 \qquad \text{(D)}\ 10 \qquad \text{(E)}\ 11$
D. 10.0
null
null
di-zhang-fdu/AOPS
false
true
33
math_hard
8007ca84-3302-5d9e-98ad-a994205734ea
$\diamondsuit$ and $\Delta$ are whole numbers and $\diamondsuit \times \Delta =36$ . The largest possible value of $\diamondsuit + \Delta$ is $\text{(A)}\ 12 \qquad \text{(B)}\ 13 \qquad \text{(C)}\ 15 \qquad \text{(D)}\ 20\ \qquad \text{(E)}\ 37$
E. 37.0
null
null
di-zhang-fdu/AOPS
false
true
34
math_hard
6c118559-3587-5453-9254-044f5767a665
$\emph{triangular number}$ is a positive integer that can be expressed in the form $t_n = 1+2+3+\cdots+n$ , for some positive integer $n$ . The three smallest triangular numbers that are also perfect squares are $t_1 = 1 = 1^2$ $t_8 = 36 = 6^2$ , and $t_{49} = 1225 = 35^2$ . What is the sum of the digits of the fourth ...
D. 18.0
null
null
di-zhang-fdu/AOPS
false
true
35
math_hard
a44affe1-93a4-5b52-9636-3806bcee8544
$\frac{(3!)!}{3!}=$ $\text{(A)}\ 1\qquad\text{(B)}\ 2\qquad\text{(C)}\ 6\qquad\text{(D)}\ 40\qquad\text{(E)}\ 120$
E. 120.0
null
null
di-zhang-fdu/AOPS
false
true
36
math_hard
6a58197c-6268-5baa-9ccd-91fb168f555c
$\frac{10^7}{5\times 10^4}=$ $\text{(A)}\ .002 \qquad \text{(B)}\ .2 \qquad \text{(C)}\ 20 \qquad \text{(D)}\ 200 \qquad \text{(E)}\ 2000$
D. 200.0
null
null
di-zhang-fdu/AOPS
false
true
37
math_hard
14a3a332-7cb4-5432-a538-96c747fcb1a6
$\frac{16+8}{4-2}=$ $\text{(A)}\ 4 \qquad \text{(B)}\ 8 \qquad \text{(C)}\ 12 \qquad \text{(D)}\ 16 \qquad \text{(E)}\ 20$
C. 12.0
null
null
di-zhang-fdu/AOPS
false
true
38
math_hard
2b4d8b39-4f13-5131-8051-324656b82cee
$\frac{1}{10}+\frac{2}{20}+\frac{3}{30} =$ $\text{(A)}\ .1 \qquad \text{(B)}\ .123 \qquad \text{(C)}\ .2 \qquad \text{(D)}\ .3 \qquad \text{(E)}\ .6$
D. 0.3
null
null
di-zhang-fdu/AOPS
false
true
39
math_hard
3a3737a8-8840-5667-bc10-9b97749b94bc
$\frac{2}{10}+\frac{4}{100}+\frac{6}{1000}=$ $\text{(A)}\ .012 \qquad \text{(B)}\ .0246 \qquad \text{(C)}\ .12 \qquad \text{(D)}\ .246 \qquad \text{(E)}\ 246$
D. 0.246
null
null
di-zhang-fdu/AOPS
false
true
40
math_hard
e3b32e6a-d1a0-55df-a391-520e31330eb1
$\frac{2}{25}=$ $\text{(A)}\ .008 \qquad \text{(B)}\ .08 \qquad \text{(C)}\ .8 \qquad \text{(D)}\ 1.25 \qquad \text{(E)}\ 12.5$
B. 0.08
null
null
di-zhang-fdu/AOPS
false
true
41
math_hard
c64fcf56-01df-5b74-aa87-270814721e28
$\left(\frac{(x+1)^{2}(x^{2}-x+1)^{2}}{(x^{3}+1)^{2}}\right)^{2}\cdot\left(\frac{(x-1)^{2}(x^{2}+x+1)^{2}}{(x^{3}-1)^{2}}\right)^{2}$ equals: $\textbf{(A)}\ (x+1)^{4}\qquad\textbf{(B)}\ (x^{3}+1)^{4}\qquad\textbf{(C)}\ 1\qquad\textbf{(D)}\ [(x^{3}+1)(x^{3}-1)]^{2}$ $\textbf{(E)}\ [(x^{3}-1)^{2}]^{2}$
C. 1.0
null
null
di-zhang-fdu/AOPS
false
true
42
math_hard
a0c63e8d-899e-5844-993d-e423d0bf5208
$\log p+\log q=\log(p+q)$ only if: $\textbf{(A) \ }p=q=\text{zero} \qquad \textbf{(B) \ }p=\frac{q^2}{1-q} \qquad \textbf{(C) \ }p=q=1 \qquad$ $\textbf{(D) \ }p=\frac{q}{q-1} \qquad \textbf{(E) \ }p=\frac{q}{q+1}$
D. 1.0
null
null
di-zhang-fdu/AOPS
false
true
43
math_hard
c1e8442f-6bae-51cc-a371-1c102951c651
$\text{palindrome}$ , such as $83438$ , is a number that remains the same when its digits are reversed. The numbers $x$ and $x+32$ are three-digit and four-digit palindromes, respectively. What is the sum of the digits of $x$ $\textbf{(A)}\ 20 \qquad \textbf{(B)}\ 21 \qquad \textbf{(C)}\ 22 \qquad \textbf{(D)}\ 23 \qqu...
E. 24.0
null
null
di-zhang-fdu/AOPS
false
true
44
math_hard
8af45d76-cf54-5dea-8d50-d01ebfd974dd
$\triangle ABC$ has a right angle at $C$ and $\angle A = 20^\circ$ . If $BD$ $D$ in $\overline{AC}$ ) is the bisector of $\angle ABC$ , then $\angle BDC =$ $\textbf{(A)}\ 40^\circ \qquad \textbf{(B)}\ 45^\circ \qquad \textbf{(C)}\ 50^\circ \qquad \textbf{(D)}\ 55^\circ\qquad \textbf{(E)}\ 60^\circ$
D. 55.0
null
null
di-zhang-fdu/AOPS
false
true
45
math_hard
08ecaa27-c6ce-50a7-8bf7-7b09b4e8b238
$\triangle$ or $\bigcirc$ is placed in each of the nine squares in a $3$ -by- $3$ grid. Shown below is a sample configuration with three $\triangle$ s in a line. [asy] //diagram size(5cm); defaultpen(linewidth(1.5)); real r = 0.37; path equi = r * dir(-30) -- (r+0.03) * dir(90) -- r * dir(210) -- cycle; draw((0,0)--(0,...
D. 84.0
null
null
di-zhang-fdu/AOPS
false
true
46
math_hard
fd63b51d-6040-596d-9c42-d328d6c6c0c4
A "stair-step" figure is made of alternating black and white squares in each row. Rows $1$ through $4$ are shown. All rows begin and end with a white square. The number of black squares in the $37\text{th}$ row is [asy] draw((0,0)--(7,0)--(7,1)--(0,1)--cycle); draw((1,0)--(6,0)--(6,2)--(1,2)--cycle); draw((2,0)--(5,0)-...
C. 36.0
null
null
di-zhang-fdu/AOPS
false
true
47
math_hard
08c17b0c-0394-5c94-a293-18d5b279e429
A 100 foot long moving walkway moves at a constant rate of 6 feet per second. Al steps onto the start of the walkway and stands. Bob steps onto the start of the walkway two seconds later and strolls forward along the walkway at a constant rate of 4 feet per second. Two seconds after that, Cy reaches the start of the...
52.0
null
null
di-zhang-fdu/AOPS
false
true
48
math_hard
84a67173-e317-51f9-893d-3e498a7025d4
A 16-step path is to go from $(-4,-4)$ to $(4,4)$ with each step increasing either the $x$ -coordinate or the $y$ -coordinate by 1. How many such paths stay outside or on the boundary of the square $-2 \le x \le 2$ $-2 \le y \le 2$ at each step? $\textbf{(A)}\ 92 \qquad \textbf{(B)}\ 144 \qquad \textbf{(C)}\ 1568 \qqua...
D. 1698.0
null
null
di-zhang-fdu/AOPS
false
true
49
math_hard
b2b3cfd9-e97a-5061-937e-30a6059d3697
A 3x3x3 cube is made of $27$ normal dice. Each die's opposite sides sum to $7$ . What is the smallest possible sum of all of the values visible on the $6$ faces of the large cube? $\text{(A)}\ 60 \qquad \text{(B)}\ 72 \qquad \text{(C)}\ 84 \qquad \text{(D)}\ 90 \qquad \text{(E)} 96$
D. 90.0
null
null
di-zhang-fdu/AOPS
false
true
50
math_hard
012b1bd6-1c10-5b82-93a5-9da5f4befcbc
A bag contains only blue balls and green balls. There are $6$ blue balls. If the probability of drawing a blue ball at random from this bag is $\frac{1}{4}$ , then the number of green balls in the bag is $\text{(A)}\ 12 \qquad \text{(B)}\ 18 \qquad \text{(C)}\ 24 \qquad \text{(D)}\ 30 \qquad \text{(E)}\ 36$
B. 18.0
null
null
di-zhang-fdu/AOPS
false
true
51
math_hard
4a5450d1-e4b8-5b4e-a28f-5a304f7e3b0d
A ball is dropped from a height of $3$ meters. On its first bounce it rises to a height of $2$ meters. It keeps falling and bouncing to $\frac{2}{3}$ of the height it reached in the previous bounce. On which bounce will it not rise to a height of $0.5$ meters? $\textbf{(A)}\ 3 \qquad \textbf{(B)}\ 4 \qquad \textbf{(C...
C. 5.0
null
null
di-zhang-fdu/AOPS
false
true
52
math_hard
89f98f65-8450-5a0e-a0aa-7adad53bb93c
A bank charges $\textdollar{6}$ for a loan of $\textdollar{120}$ . The borrower receives $\textdollar{114}$ and repays the loan in $12$ easy installments of $\textdollar{10}$ a month. The interest rate is approximately: $\textbf{(A)}\ 5 \% \qquad \textbf{(B)}\ 6 \% \qquad \textbf{(C)}\ 7 \% \qquad \textbf{(D)}\ 9\% \qq...
A. 5.0
null
null
di-zhang-fdu/AOPS
false
true
53
math_hard
f692649d-0d4c-5b2f-9e36-fd43b7ae7421
A bar graph shows the number of hamburgers sold by a fast food chain each season. However, the bar indicating the number sold during the winter is covered by a smudge. If exactly $25\%$ of the chain's hamburgers are sold in the fall, how many million hamburgers are sold in the winter? [asy] size(250); void bargraph(...
A. 2.5
null
null
di-zhang-fdu/AOPS
false
true
54
math_hard
71ec20e9-0da1-52e3-9f44-69f53422dadf
A barn with a roof is rectangular in shape, $10$ yd. wide, $13$ yd. long and $5$ yd. high. It is to be painted inside and outside, and on the ceiling, but not on the roof or floor. The total number of sq. yd. to be painted is: $\mathrm{(A) \ } 360 \qquad \mathrm{(B) \ } 460 \qquad \mathrm{(C) \ } 490 \qquad \mathrm{(D...
D. 590.0
null
null
di-zhang-fdu/AOPS
false
true
55
math_hard
b21eb127-cd58-53cb-b0df-3a8385d14829
A base-10 three digit number $n$ is selected at random. Which of the following is closest to the probability that the base-9 representation and the base-11 representation of $n$ are both three-digit numerals? $\mathrm{(A) \ } 0.3\qquad \mathrm{(B) \ } 0.4\qquad \mathrm{(C) \ } 0.5\qquad \mathrm{(D) \ } 0.6\qquad \mathr...
E. 0.7
null
null
di-zhang-fdu/AOPS
false
true
56
math_hard
1caef5a0-9966-558b-b21d-33d1d0f7df36
A baseball league consists of two four-team divisions. Each team plays every other team in its division $N$ games. Each team plays every team in the other division $M$ games with $N>2M$ and $M>4$ . Each team plays a $76$ game schedule. How many games does a team play within its own division? $\textbf{(A) } 36 \qquad \t...
B. 48.0
null
null
di-zhang-fdu/AOPS
false
true
57
math_hard
e25571e2-98b2-56e1-938d-bd69d08365de
A basketball player has a constant probability of $.4$ of making any given shot, independent of previous shots. Let $a_n$ be the ratio of shots made to shots attempted after $n$ shots. The probability that $a_{10} = .4$ and $a_n\le.4$ for all $n$ such that $1\le n\le9$ is given to be $p^aq^br/\left(s^c\right)$ where $p...
660.0
null
null
di-zhang-fdu/AOPS
false
true
58
math_hard
87b8fc5c-0d86-5382-b6aa-51d7451181b2
A basketball player made 5 baskets during a game. Each basket was worth either 2 or 3 points. How many different numbers could represent the total points scored by the player? $\mathrm{(A)}\ 2\qquad\mathrm{(B)}\ 3\qquad\mathrm{(C)}\ 4\qquad\mathrm{(D)}\ 5\qquad\mathrm{(E)}\ 6$
E. 6.0
null
null
di-zhang-fdu/AOPS
false
true
59
math_hard
52bf4399-fe93-5b0b-8768-b95ab8a00015
A basketball team's players were successful on 50% of their two-point shots and 40% of their three-point shots, which resulted in 54 points. They attempted 50% more two-point shots than three-point shots. How many three-point shots did they attempt? $\textbf{(A) }10\qquad\textbf{(B) }15\qquad\textbf{(C) }20\qquad\textb...
C. 20.0
null
null
di-zhang-fdu/AOPS
false
true
60
math_hard
05210e1a-d9d2-5eb7-91f5-8d9eb9f68da5
A beam of light strikes $\overline{BC}\,$ at point $C\,$ with angle of incidence $\alpha=19.94^\circ\,$ and reflects with an equal angle of reflection as shown. The light beam continues its path, reflecting off line segments $\overline{AB}\,$ and $\overline{BC}\,$ according to the rule: angle of incidence equals angle...
71.0
null
null
di-zhang-fdu/AOPS
false
true
61
math_hard
6bf7cbdd-f0ea-59e9-ac45-abc09468c375
A bee starts flying from point $P_0$ . She flies $1$ inch due east to point $P_1$ . For $j \ge 1$ , once the bee reaches point $P_j$ , she turns $30^{\circ}$ counterclockwise and then flies $j+1$ inches straight to point $P_{j+1}$ . When the bee reaches $P_{2015}$ she is exactly $a \sqrt{b} + c \sqrt{d}$ inches away fr...
B. 2024.0
null
null
di-zhang-fdu/AOPS
false
true
62
math_hard
aea48f8f-2007-50b5-bfcf-c98980d20a37
A binary operation $\diamondsuit$ has the properties that $a\,\diamondsuit\, (b\,\diamondsuit \,c) = (a\,\diamondsuit \,b)\cdot c$ and that $a\,\diamondsuit \,a=1$ for all nonzero real numbers $a, b,$ and $c$ . (Here $\cdot$ represents multiplication). The solution to the equation $2016 \,\diamondsuit\, (6\,\diamondsui...
A. 109.0
null
null
di-zhang-fdu/AOPS
false
true
63
math_hard
95fba5b3-c49d-520c-ba2c-6684c9bbbb11
A biologist wants to calculate the number of fish in a lake. On May 1 she catches a random sample of 60 fish, tags them, and releases them. On September 1 she catches a random sample of 70 fish and finds that 3 of them are tagged. To calculate the number of fish in the lake on May 1, she assumes that 25% of these fish ...
840.0
null
null
di-zhang-fdu/AOPS
false
true
64
math_hard
d3e6bdd8-e8ac-53d2-bc4e-77899de6f896
A block of cheese in the shape of a rectangular solid measures $10$ cm by $13$ cm by $14$ cm. Ten slices are cut from the cheese. Each slice has a width of $1$ cm and is cut parallel to one face of the cheese. The individual slices are not necessarily parallel to each other. What is the maximum possible volume in cubic...
729.0
null
null
di-zhang-fdu/AOPS
false
true
65
math_hard
96811a09-912b-5ad4-904f-bebeb6fe83e9
A block of wood has the shape of a right circular cylinder with radius $6$ and height $8$ , and its entire surface has been painted blue. Points $A$ and $B$ are chosen on the edge of one of the circular faces of the cylinder so that $\overarc{AB}$ on that face measures $120^\circ$ . The block is then sliced in half a...
53.0
null
null
di-zhang-fdu/AOPS
false
true
66
math_hard
58a600ca-0d10-5f18-aee4-a5757e4f0011
A block wall 100 feet long and 7 feet high will be constructed using blocks that are 1 foot high and either 2 feet long or 1 foot long (no blocks may be cut). The vertical joins in the blocks must be staggered as shown, and the wall must be even on the ends. What is the smallest number of blocks needed to build this wa...
D. 353.0
null
null
di-zhang-fdu/AOPS
false
true
67
math_hard
a135973b-7bfb-5646-8f44-eafa2fd357d8
A board game spinner is divided into three regions labeled $A$ $B$ and $C$ . The probability of the arrow stopping on region $A$ is $\frac{1}{3}$ and on region $B$ is $\frac{1}{2}$ . The probability of the arrow stopping on region $C$ is: $\text{(A)}\ \frac{1}{12}\qquad\text{(B)}\ \frac{1}{6}\qquad\text{(C)}\ \frac{1}{...
B. 16.0
null
null
di-zhang-fdu/AOPS
false
true
68
math_hard
9d77444c-1d6e-5140-9f6e-cc7ca66505f9
A book that is to be recorded onto compact discs takes $412$ minutes to read aloud. Each disc can hold up to $56$ minutes of reading. Assume that the smallest possible number of discs is used and that each disc contains the same length of reading. How many minutes of reading will each disc contain? $\mathrm{(A)}\ 50.2 ...
B. 51.5
null
null
di-zhang-fdu/AOPS
false
true
69
math_hard
627260f4-7af0-524e-9ad2-be689fd0314c
A bored student walks down a hall that contains a row of closed lockers, numbered $1$ to $1024$ . He opens the locker numbered 1, and then alternates between skipping and opening each locker thereafter. When he reaches the end of the hall, the student turns around and starts back. He opens the first closed locker he en...
342.0
null
null
di-zhang-fdu/AOPS
false
true
70
math_hard
8ad4ef9c-1cf7-5cd3-90b0-80a264443669
A bowl is formed by attaching four regular hexagons of side $1$ to a square of side $1$ . The edges of the adjacent hexagons coincide, as shown in the figure. What is the area of the octagon obtained by joining the top eight vertices of the four hexagons, situated on the rim of the bowl? [asy] import three; size(225); ...
B. 7.0
null
null
di-zhang-fdu/AOPS
false
true
71
math_hard
9c7ec036-cbeb-561b-a2fb-3e37b28d0b71
A box $2$ centimeters high, $3$ centimeters wide, and $5$ centimeters long can hold $40$ grams of clay. A second box with twice the height, three times the width, and the same length as the first box can hold $n$ grams of clay. What is $n$ $\textbf{(A)}\ 120\qquad\textbf{(B)}\ 160\qquad\textbf{(C)}\ 200\qquad\textbf{...
D. 240.0
null
null
di-zhang-fdu/AOPS
false
true
72
math_hard
71696a7e-9222-548c-9a55-76d9aa25d5bd
A box contains $28$ red balls, $20$ green balls, $19$ yellow balls, $13$ blue balls, $11$ white balls, and $9$ black balls. What is the minimum number of balls that must be drawn from the box without replacement to guarantee that at least $15$ balls of a single color will be drawn? $\textbf{(A) } 75 \qquad\textbf{(B) }...
B. 76.0
null
null
di-zhang-fdu/AOPS
false
true
73
math_hard
e31da722-688a-5429-a8d4-14b238adc5cd
A box contains a collection of triangular and square tiles. There are $25$ tiles in the box, containing $84$ edges total. How many square tiles are there in the box? $\textbf{(A)}\ 3\qquad\textbf{(B)}\ 5\qquad\textbf{(C)}\ 7\qquad\textbf{(D)}\ 9\qquad\textbf{(E)}\ 11$
D. 9.0
null
null
di-zhang-fdu/AOPS
false
true
74
math_hard
9463074b-a029-54ef-86dc-f393716184d2
A box contains chips, each of which is red, white, or blue. The number of blue chips is at least half the number of white chips, and at most one third the number of red chips. The number which are white or blue is at least $55$ . The minimum number of red chips is $\textbf{(A) }24\qquad \textbf{(B) }33\qquad \textbf{(C...
57.0
null
null
di-zhang-fdu/AOPS
false
true
75
math_hard
8bcfa93d-d731-5b9b-8800-c98c75d73e9a
A box contains gold coins. If the coins are equally divided among six people, four coins are left over. If the coins are equally divided among five people, three coins are left over. If the box holds the smallest number of coins that meets these two conditions, how many coins are left when equally divided among seven p...
A. 0.0
null
null
di-zhang-fdu/AOPS
false
true
76
math_hard
5099507d-eec1-5c05-8d68-86010fa50af7
A boy buys oranges at $3$ for $10$ cents. He will sell them at $5$ for $20$ cents. In order to make a profit of $$1.00$ , he must sell: $\textbf{(A)}\ 67 \text{ oranges} \qquad \textbf{(B)}\ 150 \text{ oranges} \qquad \textbf{(C)}\ 200\text{ oranges}\\ \textbf{(D)}\ \text{an infinite number of oranges}\qquad \textbf{(...
B. 150.0
null
null
di-zhang-fdu/AOPS
false
true
77
math_hard
60b1f578-dcd6-5ee8-9956-517f622be40c
A bug crawls along a number line, starting at $-2$ . It crawls to $-6$ , then turns around and crawls to $5$ . How many units does the bug crawl altogether? $\textbf{(A)}\ 9\qquad\textbf{(B)}\ 11\qquad\textbf{(C)}\ 13\qquad\textbf{(D)}\ 14\qquad\textbf{(E)}\ 15$
E. 15.0
null
null
di-zhang-fdu/AOPS
false
true
78
math_hard
f90617c2-cebc-5d10-93bb-46f11fd229bd
A bug starts at a vertex of an equilateral triangle. On each move, it randomly selects one of the two vertices where it is not currently located, and crawls along a side of the triangle to that vertex. Given that the probability that the bug moves to its starting vertex on its tenth move is $m/n,$ where $m$ and $n$ are...
683.0
null
null
di-zhang-fdu/AOPS
false
true
79
math_hard
2ad9157e-8644-581f-8cd4-e7bda0eae543
A bug travels from A to B along the segments in the hexagonal lattice pictured below. The segments marked with an arrow can be traveled only in the direction of the arrow, and the bug never travels the same segment more than once. How many different paths are there? [asy] size(10cm); draw((0.0,0.0)--(1.0,1.732050807568...
E. 2400.0
null
null
di-zhang-fdu/AOPS
false
true
80
math_hard
12371aa3-007d-55e4-828c-46e06db82a36
A bug travels in the coordinate plane, moving only along the lines that are parallel to the $x$ -axis or $y$ -axis. Let $A = (-3, 2)$ and $B = (3, -2)$ . Consider all possible paths of the bug from $A$ to $B$ of length at most $20$ . How many points with integer coordinates lie on at least one of these paths? $\textbf{...
C. 195.0
null
null
di-zhang-fdu/AOPS
false
true
81
math_hard
4f1689cd-4e93-5142-9a07-0bdac36960e4
A bug walks all day and sleeps all night. On the first day, it starts at point $O$ , faces east, and walks a distance of $5$ units due east. Each night the bug rotates $60^\circ$ counterclockwise. Each day it walks in this new direction half as far as it walked the previous day. The bug gets arbitrarily close to the po...
103.0
null
null
di-zhang-fdu/AOPS
false
true
82
math_hard
7f9b52a5-4490-591b-b494-459ef978fe41
A burger at Ricky C's weighs $120$ grams, of which $30$ grams are filler. What percent of the burger is not filler? $\mathrm{(A)}\ 60\% \qquad\mathrm{(B)}\ 65\% \qquad\mathrm{(C)}\ 70\% \qquad\mathrm{(D)}\ 75\% \qquad\mathrm{(E)}\ 90\%$
D. 75.0
null
null
di-zhang-fdu/AOPS
false
true
83
math_hard
395b5749-314e-5422-a70e-224e80d5c84b
A bus takes $2$ minutes to drive from one stop to the next, and waits $1$ minute at each stop to let passengers board. Zia takes $5$ minutes to walk from one bus stop to the next. As Zia reaches a bus stop, if the bus is at the previous stop or has already left the previous stop, then she will wait for the bus. Otherwi...
A. 17.0
null
null
di-zhang-fdu/AOPS
false
true
84
math_hard
39208e5e-3340-5169-a475-9b7304e8bade
A can of soup can feed $3$ adults or $5$ children. If there are $5$ cans of soup and $15$ children are fed, then how many adults would the remaining soup feed? $\text{(A)}\ 5 \qquad \text{(B)}\ 6 \qquad \text{(C)}\ 7 \qquad \text{(D)}\ 8 \qquad \text{(E)}\ 10$
B. 6.0
null
null
di-zhang-fdu/AOPS
false
true
85
math_hard
741bbfd7-cce3-5b34-99f3-9a2a42a85379
A car travels $120$ miles from $A$ to $B$ at $30$ miles per hour but returns the same distance at $40$ miles per hour. The average speed for the round trip is closest to: $\textbf{(A)}\ 33\text{ mph}\qquad\textbf{(B)}\ 34\text{ mph}\qquad\textbf{(C)}\ 35\text{ mph}\qquad\textbf{(D)}\ 36\text{ mph}\qquad\textbf{(E)}\ 37...
B. 34.0
null
null
di-zhang-fdu/AOPS
false
true
86
math_hard
2d0f07ac-9773-5ebd-9ed7-62beee9b0157
A car travels due east at $\frac 23$ mile per minute on a long, straight road. At the same time, a circular storm, whose radius is $51$ miles, moves southeast at $\frac 12\sqrt{2}$ mile per minute. At time $t=0$ , the center of the storm is $110$ miles due north of the car. At time $t=t_1$ minutes, the car enters the s...
198.0
null
null
di-zhang-fdu/AOPS
false
true
87
math_hard
77e713d9-5265-583f-b86a-0b6e1eb96d79
A cart rolls down a hill, travelling $5$ inches the first second and accelerating so that during each successive $1$ -second time interval, it travels $7$ inches more than during the previous $1$ -second interval. The cart takes $30$ seconds to reach the bottom of the hill. How far, in inches, does it travel? $\textbf{...
D. 3195.0
null
null
di-zhang-fdu/AOPS
false
true
88
math_hard
792e5632-f0fe-5a62-b144-1663d9a4aeae
A cell phone plan costs $20$ dollars each month, plus $5$ cents per text message sent, plus $10$ cents for each minute used over $30$ hours. In January Michelle sent $100$ text messages and talked for $30.5$ hours. How much did she have to pay? $\textbf{(A)}\ 24.00 \qquad \textbf{(B)}\ 24.50 \qquad \textbf{(C)}\ 25.50 ...
D. 28.0
null
null
di-zhang-fdu/AOPS
false
true
89
math_hard
c1f4f07a-f460-5f19-8534-5157958c5098
A certain calculator has only two keys [+1] and [x2]. When you press one of the keys, the calculator automatically displays the result. For instance, if the calculator originally displayed "9" and you pressed [+1], it would display "10." If you then pressed [x2], it would display "20." Starting with the display "1," w...
B. 9.0
null
null
di-zhang-fdu/AOPS
false
true
90
math_hard
9e0009ea-2a6b-58cd-bed6-e1585dc710c0
A certain function $f$ has the properties that $f(3x) = 3f(x)$ for all positive real values of $x$ , and that $f(x) = 1-|x-2|$ for $1\le x \le 3$ . Find the smallest $x$ for which $f(x) = f(2001)$
429.0
null
null
di-zhang-fdu/AOPS
false
true
91
math_hard
95459808-4973-5788-80a0-6778b418bca4
A checkerboard consists of one-inch squares. A square card, $1.5$ inches on a side, is placed on the board so that it covers part or all of the area of each of $n$ squares. The maximum possible value of $n$ is $\text{(A)}\ 4\text{ or }5 \qquad \text{(B)}\ 6\text{ or }7\qquad \text{(C)}\ 8\text{ or }9 \qquad \text{(D)...
E. 12.0
null
null
di-zhang-fdu/AOPS
false
true
92
math_hard
0dc1fdf5-3b6e-57d9-b893-5c2a66fe5d0b
A checkerboard of $13$ rows and $17$ columns has a number written in each square, beginning in the upper left corner, so that the first row is numbered $1,2,\ldots,17$ , the second row $18,19,\ldots,34$ , and so on down the board. If the board is renumbered so that the left column, top to bottom, is $1,2,\ldots,13,$ , ...
D. 555.0
null
null
di-zhang-fdu/AOPS
false
true
93
math_hard
5bea085f-604c-5443-95b8-4a6022573278
A chess king is said to attack all the squares one step away from it, horizontally, vertically, or diagonally. For instance, a king on the center square of a $3$ $3$ grid attacks all $8$ other squares, as shown below. Suppose a white king and a black king are placed on different squares of a $3$ $3$ grid so that they d...
E. 32.0
null
null
di-zhang-fdu/AOPS
false
true
94
math_hard
3645f04b-6786-58d6-bd0e-7391cb1e9f29
A child builds towers using identically shaped cubes of different colors. How many different towers with a height $8$ cubes can the child build with $2$ red cubes, $3$ blue cubes, and $4$ green cubes? (One cube will be left out.) $\textbf{(A) } 24 \qquad\textbf{(B) } 288 \qquad\textbf{(C) } 312 \qquad\textbf{(D) } 1,26...
D. 1260.0
null
null
di-zhang-fdu/AOPS
false
true
95
math_hard
19ff9fba-e335-5ed1-957e-5ef7f365817e
A child has a set of $96$ distinct blocks. Each block is one of $2$ materials (plastic, wood), $3$ sizes (small, medium, large), $4$ colors (blue, green, red, yellow), and $4$ shapes (circle, hexagon, square, triangle). How many blocks in the set differ from the 'plastic medium red circle' in exactly $2$ ways? (The 'wo...
29.0
null
null
di-zhang-fdu/AOPS
false
true
96
math_hard
713bf123-3385-5da5-95bd-80135642d2e2
A child's wading pool contains 200 gallons of water. If water evaporates at the rate of 0.5 gallons per day and no other water is added or removed, how many gallons of water will be in the pool after 30 days? $\text{(A)}\ 140 \qquad \text{(B)}\ 170 \qquad \text{(C)}\ 185 \qquad \text{(D)}\ 198.5 \qquad \text{(E)}\ 199...
C. 185.0
null
null
di-zhang-fdu/AOPS
false
true
97
math_hard
263da4d2-fbd0-5bc8-93ae-fbda37a1b772
A circle centered at $A$ with a radius of 1 and a circle centered at $B$ with a radius of 4 are externally tangent. A third circle is tangent to the first two and to one of their common external tangents as shown. What is the radius of the third circle? [asy] unitsize(0.75cm); pair A=(0,1), B=(4,4); dot(A); dot(B); dra...
49.0
null
null
di-zhang-fdu/AOPS
false
true
98
math_hard
2acf0ab3-cb42-5950-9172-3fcb150252fd
A circle has a chord of length $10$ , and the distance from the center of the circle to the chord is $5$ . What is the area of the circle? $\textbf{(A) }25\pi \qquad \textbf{(B) }50\pi \qquad \textbf{(C) }75\pi \qquad \textbf{(D) }100\pi \qquad \textbf{(E) }125\pi \qquad$
B. 50.0
null
null
di-zhang-fdu/AOPS
false
true
99
math_hard
dbded014-32ae-596d-af86-7b56776e802e
A circle has center $(-10, -4)$ and has radius $13$ . Another circle has center $(3, 9)$ and radius $\sqrt{65}$ . The line passing through the two points of intersection of the two circles has equation $x+y=c$ . What is $c$ $\textbf{(A)}\ 3\qquad\textbf{(B)}\ 3\sqrt{3}\qquad\textbf{(C)}\ 4\sqrt{2}\qquad\textbf{(D)}\ 6\...
A. 3.0
null
null
di-zhang-fdu/AOPS
false
true
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