## 2014 AIME II真题

#### 答案解析请参考文末

## Problem 1

Abe can paint the room in 15 hours, Bea can paint 50 percent faster than Abe, and Coe can paint twice as fast as Abe. Abe begins to paint the room and works alone for the first hour and a half. Then Bea joins Abe, and they work together until half the room is painted. Then Coe joins Abe and Bea, and they work together until the entire room is painted. Find the number of minutes after Abe begins for the three of them to finish painting the room.

## Problem 2

Arnold is studying the prevalence of three health risk factors, denoted by A, B, and C, within a population of men. For each of the three factors, the probability that a randomly selected man in the population has only this risk factor (and none of the others) is 0.1. For any two of the three factors, the probability that a randomly selected man has exactly these two risk factors (but not the third) is 0.14. The probability that a randomly selected man has all three risk factors, given that he has A and B is . The probability that a man has none of the three risk factors given that he does not have risk factor A is , where and are relatively prime positive integers. Find .

## Problem 3

A rectangle has sides of length and 36. A hinge is installed at each vertex of the rectangle, and at the midpoint of each side of length 36. The sides of length can be pressed toward each other keeping those two sides parallel so the rectangle becomes a convex hexagon as shown. When the figure is a hexagon with the sides of length parallel and separated by a distance of 24, the hexagon has the same area as the original rectangle. Find .

## Problem 4

The repeating decimals and satisfy

where , , and are (not necessarily distinct) digits. Find the three digit number .

## Problem 5

Real numbers and are roots of , and and are roots of . Find the sum of all possible values of .

## Problem 6

Charles has two six-sided dice. One of the die is fair, and the other die is biased so that it comes up six with probability and each of the other five sides has probability . Charles chooses one of the two dice at random and rolls it three times. Given that the first two rolls are both sixes, the probability that the third roll will also be a six is , where and are relatively prime positive integers. Find .

## Problem 7

Let . Find the sum of all positive integers for which

## Problem 8

Circle with radius 2 has diameter . Circle is internally tangent to circle at . Circle is internally tangent to circle , externally tangent to circle , and tangent to . The radius of circle is three times the radius of circle , and can be written in the form , where and are positive integers. Find .

## Problem 9

Ten chairs are arranged in a circle. Find the number of subsets of this set of chairs that contain at least three adjacent chairs.

## Problem 10

Let be a complex number with . Let be the polygon in the complex plane whose vertices are and every such that . Then the area enclosed by can be written in the form , where is an integer. Find the remainder when is divided by .

## Problem 11

In , and . . Let be the midpoint of segment . Point lies on side such that . Extend segment through to point such that . Then , where and are relatively prime positive integers, and is a positive integer. Find .

## Problem 12

Suppose that the angles of satisfy . Two sides of the triangle have lengths 10 and 13. There is a positive integer so that the maximum possible length for the remaining side of is . Find .

## Problem 13

Ten adults enter a room, remove their shoes, and toss their shoes into a pile. Later, a child randomly pairs each left shoe with a right shoe without regard to which shoes belong together. The probability that for every positive integer , no collection of pairs made by the child contains the shoes from exactly of the adults is , where and are relatively prime positive integers. Find .

## Problem 14

In , , , and . Let , , and be points on line such that , , and . Point is the midpoint of segment, and point is on ray such that . Then , where and are relatively prime positive integers. Find .

## Problem 15

For any integer , let be the smallest prime which does not divide . Define the integer function to be the product of all primes less than if , and if . Let be the sequence defined by , and for . Find the smallest positive integer such that .

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