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1999 AIME Problems

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1999 AIME (Answer Key)
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Instructions

  1. This is a 15-question, 3-hour examination. All answers are integers ranging from 000 to 999, inclusive. Your score will be the number of correct answers; i.e., there is neither partial credit nor a penalty for wrong answers.
  2. No aids other than scratch paper, graph paper, ruler, compass, and protractor are permitted. In particular, calculators are not permitted.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Contents

Problem 1

Find the smallest prime that is the fifth term of an increasing arithmetic sequence, all four preceding terms also being prime.

Solution

Problem 2

Consider the parallelogram with vertices (10,45), (10,114), (28,153), and (28,84). A line through the origin cuts this figure into two congruent polygons. The slope of the line is m/n, where m_{} and n_{} are relatively prime positive integers. Find m+n.

Solution

Problem 3

Find the sum of all positive integers n for which n^2-19n+99 is a perfect square.

Solution

Problem 4

The two squares shown share the same center O_{} and have sides of length 1. The length of \overline{AB} is 43/99 and the area of octagon ABCDEFGH is m/n, where m_{} and n_{} are relatively prime positive integers. Find m+n.

Image:AIME_1999_Problem_4.png

Solution

Problem 5

For any positive integer x_{}, let S(x) be the sum of the digits of x_{}, and let T(x) be |S(x+2)-S(x)|. For example, T(199)=|S(201)-S(199)|=|3-19|=16. How many values T(x) do not exceed 1999?

Solution

Problem 6

A transformation of the first quadrant of the coordinate plane maps each point (x,y) to the point (\sqrt{x},\sqrt{y}). The vertices of quadrilateral ABCD are A=(900,300), B=(1800,600), C=(600,1800), and D=(300,900). Let k_{} be the area of the region enclosed by the image of quadrilateral ABCD. Find the greatest integer that does not exceed k_{}.

Solution

Problem 7

There is a set of 1000 switches, each of which has four positions, called A, B, C, and D. When the position of any switch changes, it is only from A to B, from B to C, from C to D, or from D to A. Initially each switch is in position A. The switches are labeled with the 1000 different integers (2^{x})(3^{y})(5^{z}), where x, y, and z take on the values 0, 1, \ldots, 9. At step i of a 1000-step process, the i-th switch is advanced one step, and so are all the other switches whose labels divide the label on the i-th switch. After step 1000 has been completed, how many switches will be in position A?

Solution

Problem 8

Let \mathcal{T} be the set of ordered triples (x,y,z) of nonnegative real numbers that lie in the plane x+y+z=1. Let us say that (x,y,z) supports (a,b,c) when exactly two of the following are true: x\ge a, y\ge b, z\ge c. Let \mathcal{S} consist of those triples in \mathcal{T} that support \left(\frac 12,\frac 13,\frac 16\right). The area of \mathcal{S} divided by the area of \mathcal{T} is m/n, where m_{} and n_{} are relatively prime positive integers, find m+n.

Solution

Problem 9

A function f is defined on the complex numbers by f(z)=(a+bi)z, where a_{} and b_{} are positive numbers. This function has the property that the image of each point in the complex plane is equidistant from that point and the origin. Given that |a+bi|=8 and that b^2=m/n, where m_{} and n_{} are relatively prime positive integers. Find m+n.

Solution

Problem 10

Ten points in the plane are given, with no three collinear. Four distinct segments joining pairs of these points are chosen at random, all such segments being equally likely. The probability that some three of the segments form a triangle whose vertices are among the ten given points is m/n, where m_{} and n_{} are relatively prime positive integers. Find m+n.

Solution

Problem 11

Given that \sum_{k=1}^{35}\sin 5k=\tan \frac mn, where angles are measured in degrees, and m_{} and n_{} are relatively prime positive integers that satisfy \frac mn<90, find m+n.

Solution

Problem 12

The inscribed circle of triangle ABC is tangent to \overline{AB} at P_{}, and its radius is 21. Given that AP=23 and PB=27, find the perimeter of the triangle.

Solution

Problem 13

Forty teams play a tournament in which every team plays every other team exactly once. No ties occur, and each team has a 50 \% chance of winning any game it plays. The probability that no two teams win the same number of games is m/n, where m_{} and n_{} are relatively prime positive integers. Find \log_2 n.

Solution

Problem 14

Point P_{} is located inside traingle ABC so that angles PAB, PBC, and PCA are all congruent. The sides of the triangle have lengths AB=13, BC=14, and CA=15, and the tangent of angle PAB is m/n, where m_{} and n_{} are relatively prime positive integers. Find m+n.

Solution

Problem 15

Consider the paper triangle whose vertices are (0,0), (34,0), and (16,24). The vertices of its midpoint triangle are the midpoints of its sides. A triangular pyramid is formed by folding the triangle along the sides of its midpoint triangle. What is the volume of this pyramid?

Solution

See also

Do you have what it takes to be the next brilliant trader, researcher, or developer at Jane Street Capital? Find out in the Careers in Mathematics Forum.
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