Mock AIME 2 Pre 2005 Problems

Problem 1

Compute the largest integer $k$ such that $2004^k$ divides $2004!$ .

Problem 2

$x$ is a real number with the property that $x+\tfrac1x = 3$ . Let $S_m = x^m + \tfrac{1}{x^m}$ . Determine the value of $S_7$ .

Solution

Problem 3

In a box, there are $4$ green balls, $4$ blue balls, $2$ red balls, a brown ball, a white ball, and a black ball. These balls are randomly drawn out of the box one at a time (without replacement) until two of the same color have been removed. This process requires that at most $7$ balls be removed. The probability that $7$ balls are drawn can be expressed as $\tfrac{m}{n}$ , where $m$ and $n$ are relatively prime positive integers. Compute $m+n$ .

Solution

Problem 4

Let $S = \{5^k | k \in \textbf{Z}, 0 \le k \le 2004 \}$ . Given that $5^{2004} = 5443 \cdots 0625$ has $1401$ digits, how many elements of $S$ begin with the digit $1$ ?

Solution

Problem 5

Let $S$ be the set of integers $n > 1$ for which $\tfrac1n = 0.d_1d_2d_3d_4\ldots$ , an infinite decimal that has the property that $d_i = d_{i+12}$ for all positive integers $i$ . Given that $9901$ is prime, how many positive integers are in $S$ ? (The $d_i$ are digits.)

Solution

Problem 6

$ABC$ is a scalene triangle. Points $D$ , $E$ , and $F$ are selected on sides $BC$ , $CA$ , and $AB$ respectively. The cevians $AD$ , $BE$ , and $CF$ concur at point $P$ . If $[AFP] = 126$ , $[FBP] = 63$ , and $[CEP] = 24$ , determine the area of triangle $ABC$ .

Solution

Problem 7

Anders, Po-Ru, Reid, and Aaron are playing Bridge. After one hand, they notice that all of the cards of the two suits are split between Reid and Po-Ru's hands. Let $N$ denote the number of ways $13$ cards can be dealt to each player such that this is the case. Determine the remainder obtained when $N$ is divided by $1000$ . (Bridge is a game played with the standard $52$ -card deck.)

Solution

Problem 8

Determine the remainder obtained when the expression $2004^{2003^{2002^{2001}}}$ is divided by $1000$ .

Solution

Problem 9

Let $(1+x^3)\left(1+2x^{3^2}\right)\cdots \left(1+kx^{3^k}\right) \cdots \left(1+1997x^{3^{1997}}\right) = 1+a_1 x^{k_1} + a_2 x^{k_2} + \cdots + a_m x^{k_m}$ where $a_i \ne 0$ and $k_1 < k_2 < \cdots < k_m$ . Determine the remainder obtained when $a_{1997}$ is divided by $1000$ .

Solution

Problem 10

$ABCDE$ is a cyclic pentagon with $BC = CD = DE$ . The diagonals $AC$ and $BE$ intersect at $M$ . $N$ is the foot of the altitude from $M$ to $AB$ . We have $MA = 25$ , $MD = 113$ , and $MN = 15$ . The area of triangle $ABE$ can be expressed as $\tfrac{m}{n}$ where $m$ and $n$ are relatively prime positive integers. Determine the remainder obtained when $m+n$ is divided by $1000$ .

Solution

Problem 11

$\alpha$ , $\beta$ , and $\gamma$ are the roots of $x(x-200)(4x+1) = 1$ . Let $\omega = \tan^{-1}(\alpha) + \tan^{-1}(\beta) + \tan^{-1} (\gamma).$ The value of $\tan(\omega)$ can be written as $\tfrac{m}{n}$ where $m$ and $n$ are relatively prime positive integers. Determine the value of $m+n$ .

Solution

Problem 12

$ABCD$ is a cyclic quadrilateral with $AB = 8$ , $BC = 4$ , $CD = 1$ , and $DA = 7$ . Let $O$ and $P$ denote the circumcenter and intersection of $AC$ and $BD$ respectively. The value of $OP^2$ can be expressed as $\tfrac{m}{n}$ , where $m$ and $n$ are relatively prime positive integers. Determine the remainder obtained when $m+n$ is divided by $1000$ .

Solution

Problem 13

$P(x)$ is a polynomial of minimal degree that satisfies $P(k) = \dfrac{1}{k(k+1)}$ for $k = 1, 2, 3, \ldots, 10$ . The value of $P(11)$ can be written as $-\tfrac{m}{n}$ , where $m$ and $n$ are relatively prime positive integers. Determine $m+n$ .

Solution

Problem 14

$3$ Elm trees, $4$ Dogwood trees, and $5$ Oak trees are to be planted in a line in front of a library such that $\begin{align*} i&) \text{ No two Elm trees are next to each other.} \\ ii&) \text{ No Dogwood tree is adjacent to an Oak tree.} \\ iii&) \text{ All of the trees are planted.} \end{align*}$ How many ways can the trees be situated in this manner?

Solution

Problem 15

In triangle $ABC$ , we have $BC = 13$ , $CA = 37$ , and $AB = 40$ . Points $D$ , $E$ , and $F$ are selected on $BC$ , $CA$ , and $AB$ respectively such that $AD$ , $BE$ , and $CF$ concur at the circumcenter of $ABC$ . The value of $\dfrac{1}{AD} + \dfrac{1}{BE} + \dfrac{1}{CF}$ can be expressed as $\tfrac{m}{n}$ where $m$ and $n$ are relatively prime positive integers. Determine $m+n$ .