# Difference between revisions of "1999 AIME Problems"

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== Problem 5 == | == Problem 5 == | ||

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

[[1999 AIME Problems/Problem 5|Solution]] | [[1999 AIME Problems/Problem 5|Solution]] |

## Revision as of 00:47, 22 January 2007

## Contents

## Problem 1

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

## Problem 2

Consider the parallelogram with vertices and A line through the origin cuts this figure into two congruent polygons. The slope of the line is where and are relatively prime positive integers. Find

## Problem 3

Find the sum of all positive integers for which is a perfect square.

## Problem 4

The two squares shown share the same center and have sides of length 1. The length of is and the area of octagon is where and are relatively prime positive integers. Find

## Problem 5

For any positive integer , let be the sum of the digits of , and let be For example, How many values do not exceed 1999?

## Problem 6

## Problem 7

There is a set of 1000 switches, each of which has four positions, called , and . When the position of any switch changes, it is only from to , from to , from to , or from to . Initially each switch is in position . The switches are labeled with the 1000 different integers , where , and take on the values . At step i of a 1000-step process, the -th switch is advanced one step, and so are all the other switches whose labels divide the label on the -th switch. After step 1000 has been completed, how many switches will be in position ?