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Difference between revisions of "Mock AIME II 2012 Problems"
(→‎Problem 8)
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==Problem 8==
 
==Problem 8==
 
Let <math>A</math> be a point outside circle <math>\Omega</math> with center <math>O</math> and radius <math>9</math> such that the tangents from <math>A</math> to <math>\Omega</math>, <math>AB</math> and <math>AC</math>, form <math>\angle BAO=15^{\circ}</math>. Let <math>AO</math> first intersect the circle at <math>D</math>, and extend the parallel to <math>AB</math> from <math>D</math> to meet the circle at <math>E</math>. The length <math>EC^2=m+k\sqrt{n}</math>, where <math>m</math>,<math>n</math>, and <math>k</math> are positive integers and <math>n</math> is not divisible by the square of any prime. Find <math>m+n+k</math>.
 
Let <math>A</math> be a point outside circle <math>\Omega</math> with center <math>O</math> and radius <math>9</math> such that the tangents from <math>A</math> to <math>\Omega</math>, <math>AB</math> and <math>AC</math>, form <math>\angle BAO=15^{\circ}</math>. Let <math>AO</math> first intersect the circle at <math>D</math>, and extend the parallel to <math>AB</math> from <math>D</math> to meet the circle at <math>E</math>. The length <math>EC^2=m+k\sqrt{n}</math>, where <math>m</math>,<math>n</math>, and <math>k</math> are positive integers and <math>n</math> is not divisible by the square of any prime. Find <math>m+n+k</math>.
 +
 
[[Mock AIME II 2012 Problems/Problem 8| Solution]]
 
[[Mock AIME II 2012 Problems/Problem 8| Solution]]
  

Revision as of 02:14, 5 April 2012

Problem 1

Given that \[\left(\dfrac{6^2-1}{6^2+11}\right)\left(\dfrac{7^2-2}{7^2+12}\right)\left(\dfrac{8^2-3}{8^2+13}\right)\cdots\left(\dfrac{2012^2-2007}{2012^2+2017}\right)=\dfrac{m}{n},\] where $m$ and $n$ are positive relatively prime integers, find the remainder when $m+n$ is divided by $1000$.

Solution

Problem 2

Let $\{a_n\}$ be a recursion defined such that $a_1=1, a_2=20$, and $a_n=\sqrt{\left| a_{n-1}^2-a_{n-2}^2 \right|}$ where $n\ge 3$, and $n$ is an integer. If $a_m=k$ for $k$ being a positive integer greater than $1$ and $m$ being a positive integer greater than 2, find the smallest possible value of $m+k$.

Solution

Problem 3

The $\textit{digital root}$ of a number is defined as the result obtained by repeatedly adding the digits of the number until a single digit remains. For example, the $\textit{digital root}$ of $237$ is $3$ ($2+3+7=12, 1+2=3$). Find the $\textit{digital root}$ of $2012^{2012^{2012}}$.

Solution

Problem 4

Let $\triangle ABC$ be a triangle, and let $I_A$, $I_B$, and $I_C$ be the points where the angle bisectors of $A$, $B$, and $C$, respectfully, intersect the sides opposite them. Given that $AI_B=5$, $CI_B=4$, and $CI_A=3$, then the ratio $AI_C:BI_C$ can be written in the form $m/n$ where $m$ and $n$ are positive relatively prime integers. Find $m+n$.

Solution

Problem 5

A fair die with $12$ sides numbered $1$ through $12$ inclusive is rolled $n$ times. The probability that the sum of the rolls is $2012$ is nonzero and is equivalent to the probability that a sum of $k$ is rolled. Find the minimum value of k.

Solution


Problem 6

A circle with radius $5$ and center in the first quadrant is placed so that it is tangent to the $y$-axis. If the line passing through the origin that is tangent to the circle has slope $\dfrac{1}{2}$, then the $y$-coordinate of the center of the circle can be written in the form $\dfrac{m+\sqrt{n}}{p}$ where $m$, $n$, and $p$ are positive integers, and $\text{gcd}(m,p)=1$. Find $m+n+p$.

Solution

Problem 7

Given $x, y$ are positive real numbers that satisfy $3x+4y+1=3\sqrt{x}+2\sqrt{y}$, then the value $xy$ can be expressed as $\frac{m}{n}$, where $m$ and $n$ are relatively prime positive integers. Find $m+n$. Solution

Problem 8

Let $A$ be a point outside circle $\Omega$ with center $O$ and radius $9$ such that the tangents from $A$ to $\Omega$, $AB$ and $AC$, form $\angle BAO=15^{\circ}$. Let $AO$ first intersect the circle at $D$, and extend the parallel to $AB$ from $D$ to meet the circle at $E$. The length $EC^2=m+k\sqrt{n}$, where $m$,$n$, and $k$ are positive integers and $n$ is not divisible by the square of any prime. Find $m+n+k$.

Solution

Problem 9

In $\triangle ABC$, $AB=12$, $AC=20$, and $\angle ABC=120^\circ$. $D, E,$ and $F$ lie on $\overline{AC}, \overline{AB}$, and $\overline{BC}$, respectively. If $AE=\frac{1}{4}AB, BF=\frac{1}{4}BC$, and $AD=\frac{1}{4}AC$, the area of $\triangle DEF$ can be expressed in the form $\frac{a\sqrt{b}-c\sqrt{d}}{e}$ where $a, b, c, d, e$ are all positive integers, and $b$ and $d$ do not have any perfect squares greater than $1$ as divisors. Find $a+b+c+d+e$. Solution

Problem 10

Call a set of positive integers $\mathcal{S}$ $\textit{lucky}$ if it can be split into two nonempty disjoint subsets $\mathcal{A}$ and $\mathcal{B}$ with $A\cap B=S$ such that the product of the elements in $\mathcal{A}$ and the product of the elements in $\mathcal{B}$ sum up to the cardinality of $\mathcal{S}$. Find the number of $\textit{lucky}$ sets such that the largest element is less than $15$. (Disjoint subsets have no elements in common, and the cardinality of a set is the number of elements in the set.) Solution

Problem 11

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