Found problems: 3632
2017 AMC 12/AHSME, 16
The number $21!=51,090,942,171,709,440,000$ has over $60,000$ positive integer divisors. One of them is chosen at random. What is the probability that it is odd?
$\textbf{(A)} \frac{1}{21} \qquad \textbf{(B)} \frac{1}{19} \qquad \textbf{(C)} \frac{1}{18} \qquad \textbf{(D)} \frac{1}{2} \qquad \textbf{(E)} \frac{11}{21}$
2009 AIME Problems, 9
Let $ m$ be the number of solutions in positive integers to the equation $ 4x\plus{}3y\plus{}2z\equal{}2009$, and let $ n$ be the number of solutions in positive integers to the equation $ 4x\plus{}3y\plus{}2z\equal{}2000$. Find the remainder when $ m\minus{}n$ is divided by $ 1000$.
2013 AMC 10, 19
In base $10$, the number $2013$ ends in the digit $3$. In base $9$, on the other hand, the same number is written as $(2676)_9$ and ends in the digit $6$. For how many positive integers $b$ does the base-$b$ representation of $2013$ end in the digit $3$?
$\textbf{(A) }6\qquad
\textbf{(B) }9\qquad
\textbf{(C) }13\qquad
\textbf{(D) }16\qquad
\textbf{(E) }18\qquad$
1967 AMC 12/AHSME, 27
Two candles of the same length are made of different materials so that one burns out completely at a uniform rate in $3$ hours and the other in $4$ hours. At what time P.M. should the candles be lighted so that, at 4 P.M., one stub is twice the length of the other?
$\textbf{(A)}\ 1:24\qquad
\textbf{(B)}\ 1:28\qquad
\textbf{(C)}\ 1:36\qquad
\textbf{(D)}\ 1:40\qquad
\textbf{(E)}\ 1:48$
1972 AMC 12/AHSME, 20
If $\tan x=\dfrac{2ab}{a^2-b^2}$ where $a>b>0$ and $0^\circ <x<90^\circ$, then $\sin x$ is equal to
$\textbf{(A) }\frac{a}{b}\qquad\textbf{(B) }\frac{b}{a}\qquad\textbf{(C) }\frac{\sqrt{a^2-b^2}}{2a}\qquad\textbf{(D) }\frac{\sqrt{a^2-b^2}}{2ab}\qquad \textbf{(E) }\dfrac{2ab}{a^2+b^2}$
2016 AMC 10, 6
Laura added two three-digit positive integers. All six digits in these numbers are different. Laura's sum is a three-digit number $S$. What is the smallest possible value for the sum of the digits of $S$?
$\textbf{(A)}\ 1\qquad\textbf{(B)}\ 4\qquad\textbf{(C)}\ 5\qquad\textbf{(D)}\ 15\qquad\textbf{(E)}\ 21$
1976 AMC 12/AHSME, 30
How many distinct ordered triples $(x,y,z)$ satisfy the equations \begin{align*}x+2y+4z&=12 \\ xy+4yz+2xz&=22 \\ xyz&=6~~?\end{align*}
$\textbf{(A) }\text{none}\qquad\textbf{(B) }1\qquad\textbf{(C) }2\qquad\textbf{(D) }4\qquad \textbf{(E) }6$
1964 AMC 12/AHSME, 21
If $\log_{b^2}x+\log_{x^2}b=1, b>0, b \neq 1, x \neq 1$, then $x$ equals:
$ \textbf{(A)}\ 1/b^2 \qquad\textbf{(B)}\ 1/b \qquad\textbf{(C)}\ b^2 \qquad\textbf{(D)}\ b \qquad\textbf{(E)}\ \sqrt{b} $
2015 AMC 12/AHSME, 6
Back in 1930, Tillie had to memorize her multiplication tables from $0\times 0$ through $12\times 12$. The multiplication table she was given had rows and columns labeled with the factors, and the products formed the body of the table. To the nearest hundredth, what fraction of the numbers in the body of the table are odd?
$\textbf{(A) }0.21\qquad\textbf{(B) }0.25\qquad\textbf{(C) }0.46\qquad\textbf{(D) }0.50\qquad\textbf{(E) }0.75$
2019 AIME Problems, 12
Given $f(z) = z^2-19z$, there are complex numbers $z$ with the property that $z$, $f(z)$, and $f(f(z))$ are the vertices of a right triangle in the complex plane with a right angle at $f(z)$. There are positive integers $m$ and $n$ such that one such value of $z$ is $m+\sqrt{n}+11i$. Find $m+n$.
1969 AMC 12/AHSME, 13
A circle with radius $r$ is contained within the region bounded by a circle with radius $R$. The area bounded by the larger circle is $a/b$ times the area of the region outside the smaller circle and inside the larger circle. Then $R:r$ equals:
$\textbf{(A) }\sqrt a:\sqrt b\qquad
\textbf{(B) }\sqrt a:\sqrt{a-b}\qquad
\textbf{(C) }\sqrt b:\sqrt{a-b}\qquad$
$\textbf{(D) }a:\sqrt{a-b}\qquad
\textbf{(E) }b:\sqrt{a-b}$
2021 AMC 10 Fall, 5
Let $n = 8^{2022}$. Which of the following is equal to $\frac{n}{4}$?
$\textbf{(A) }4^{1010}\qquad\textbf{(B) }2^{2022}\qquad\textbf{(C) }8^{2018}\qquad\textbf{(D) }4^{3031}\qquad\textbf{(E) }4^{3032}$
2024 AIME, 14
Let $ABCD$ be a tetrahedron such that $AB = CD = \sqrt{41}$, $AC = BD = \sqrt{80}$, and $BC = AD = \sqrt{89}$. There exists a point $I$ inside the tetrahedron such that the distances from $I$ to each of the faces of the tetrahedron are all equal. This distance can be written in the form $\frac{m \sqrt{n}}{p}$, when $m$, $n$, and $p$ are positive integers, $m$ and $p$ are relatively prime, and $n$ is not divisible by the square of any prime. Find $m+n+p$.
2017 AMC 12/AHSME, 15
Let $ABC$ be an equilateral triangle. Extend side $\overline{AB}$ beyond $B$ to a point $B'$ so that $BB' = 3AB$. Similarly, extend side $\overline{BC}$ beyond $C$ to a point $C'$ so that $CC' = 3BC$, and extend side $\overline{CA}$ beyond $A$ to a point $A'$ so that $AA' = 3CA$. What is the ratio of the area of $\triangle A'B'C'$ to the area of $\triangle ABC$?
$\textbf{(A) }9:1\qquad\textbf{(B) }16:1\qquad\textbf{(C) }25:1\qquad\textbf{(D) }36:1\qquad\textbf{(E) }37:1$
2008 AIME Problems, 6
The sequence $ \{a_n\}$ is defined by
\[ a_0 \equal{} 1,a_1 \equal{} 1, \text{ and } a_n \equal{} a_{n \minus{} 1} \plus{} \frac {a_{n \minus{} 1}^2}{a_{n \minus{} 2}}\text{ for }n\ge2.
\]The sequence $ \{b_n\}$ is defined by
\[ b_0 \equal{} 1,b_1 \equal{} 3, \text{ and } b_n \equal{} b_{n \minus{} 1} \plus{} \frac {b_{n \minus{} 1}^2}{b_{n \minus{} 2}}\text{ for }n\ge2.
\]Find $ \frac {b_{32}}{a_{32}}$.
2018 AIME Problems, 2
Let $a_0 = 2$, $a_1 = 5$, and $a_2 = 8$, and for $n>2$ define $a_n$ recursively to be the remainder when $4(a_{n-1} + a_{n-2} + a_{n-3})$ is divided by $11$. Find $a_{2018}\cdot a_{2020}\cdot a_{2022}$.
1993 AMC 8, 20
When $10^{93}-93$ is expressed as a single whole number, the sum of the digits is
$\text{(A)}\ 10 \qquad \text{(B)}\ 93 \qquad \text{(C)}\ 819 \qquad \text{(D)}\ 826 \qquad \text{(E)}\ 833$
2002 AMC 8, 16
Right isosceles triangles are constructed on the sides of a 3-4-5 right triangle, as shown. A capital letter represents the area of each triangle. Which one of the following is true?
[asy]/* AMC8 2002 #16 Problem */
draw((0,0)--(4,0)--(4,3)--cycle);
draw((4,3)--(-4,4)--(0,0));
draw((-0.15,0.1)--(0,0.25)--(.15,0.1));
draw((0,0)--(4,-4)--(4,0));
draw((4,0.2)--(3.8,0.2)--(3.8,-0.2)--(4,-0.2));
draw((4,0)--(7,3)--(4,3));
draw((4,2.8)--(4.2,2.8)--(4.2,3));
label(scale(0.8)*"$Z$", (0, 3), S);
label(scale(0.8)*"$Y$", (3,-2));
label(scale(0.8)*"$X$", (5.5, 2.5));
label(scale(0.8)*"$W$", (2.6,1));
label(scale(0.65)*"5", (2,2));
label(scale(0.65)*"4", (2.3,-0.4));
label(scale(0.65)*"3", (4.3,1.5));[/asy]
$ \textbf{(A)}\ X\plus{}Z\equal{}W\plus{}Y \qquad \textbf{(B)}\ W\plus{}X\equal{}Z \qquad\textbf{(C)}\ 3X\plus{}4Y\equal{}5Z \qquad $
$\textbf{(D)}\ X\plus{}W\equal{}\frac{1}{2}(Y\plus{}Z) \qquad\textbf{(E)}\ X\plus{}Y\equal{}Z$
2006 AIME Problems, 3
Let $P$ be the product of the first 100 positive odd integers. Find the largest integer $k$ such that $P$ is divisible by $3^k$.
2009 AMC 10, 6
A circle of radius $ 2$ is inscribed in a semicircle, as shown. The area inside the semicircle but outside the circle is shaded. What fraction of the semicircle's area is shaded?
[asy]unitsize(6mm);
defaultpen(linewidth(.8pt)+fontsize(8pt));
dotfactor=4;
filldraw(Arc((0,0),4,0,180)--cycle,gray,black);
filldraw(Circle((0,2),2),white,black);
dot((0,2));
draw((0,2)--((0,2)+2*dir(60)));
label("$2$",midpoint((0,2)--((0,2)+2*dir(60))),SE);[/asy]$ \textbf{(A)}\ \frac{1}{2}\qquad
\textbf{(B)}\ \frac{\pi}{6}\qquad
\textbf{(C)}\ \frac{2}{\pi}\qquad
\textbf{(D)}\ \frac{2}{3}\qquad
\textbf{(E)}\ \frac{3}{\pi}$
2018 AMC 12/AHSME, 10
A list of $2018$ positive integers has a unique mode, which occurs exactly $10$ times. What is the least number of distinct values that can occur in the list?
$\textbf{(A)}\ 202\qquad\textbf{(B)}\ 223\qquad\textbf{(C)}\ 224\qquad\textbf{(D)}\ 225\qquad\textbf{(E)}\ 234$
2021 AMC 10 Spring, 6
Chantal and Jean start hiking from a trailhead toward a fire tower. Jean is wearing a heavy backpack and walks slower. Chantal starts walking at $4$ miles per hour. Halfway to the tower, the trail becomes really steep, and Chantal slows down to $2$ miles per hour. After reaching the tower, she immediately turns around and descends the steep part of the trail at $3$ miles per hour. She meets Jean at the halfway point. What was Jean's average speed, in miles per hour, until they meet?
$\textbf{(A)}~\frac{12}{13}\qquad \textbf{(B)}~1\qquad \textbf{(C)}~\frac{13}{12}\qquad \textbf{(D)}~\frac{24}{13}\qquad \textbf{(E)}~2$
2010 AMC 12/AHSME, 19
Each of 2010 boxes in a line contains a single red marble, and for $ 1 \le k \le 2010$, the box in the $ kth$ position also contains $ k$ white marbles. Isabella begins at the first box and successively draws a single marble at random from each box, in order. She stops when she first draws a red marble. Let $ P(n)$ be the probability that Isabella stops after drawing exactly $ n$ marbles. What is the smallest value of $ n$ for which $ P(n) < \frac {1}{2010}$?
$ \textbf{(A)}\ 45 \qquad
\textbf{(B)}\ 63 \qquad
\textbf{(C)}\ 64 \qquad
\textbf{(D)}\ 201 \qquad
\textbf{(E)}\ 1005$
2013 AIME Problems, 2
Positive integers $a$ and $b$ satisfy the condition \[\log_2(\log_{2^a}(\log_{2^b}(2^{1000})))=0.\] Find the sum of all possible values of $a+b$.
2010 Contests, 1
Mary's top book shelf holds five books with the following widths, in centimeters: $ 6$, $ \frac12$, $ 1$, $ 2.5$, and $ 10$. What is the average book width, in centimeters?
$ \textbf{(A)}\ 1 \qquad
\textbf{(B)}\ 2 \qquad
\textbf{(C)}\ 3 \qquad
\textbf{(D)}\ 4 \qquad
\textbf{(E)}\ 5$