1988 AIME Problems/Problem 5
Problem
Let , in lowest terms, be the probability that a randomly chosen positive divisor of is an integer multiple of . Find .
Solution
, so it has factors. Out of these, we only want those factors of which are divisible by ; it is easy to draw a bijection to the number of factors that has, which is . Our probability is , and .
See also
1988 AIME (Problems • Answer Key • Resources) | ||
Preceded by Problem 4 |
Followed by Problem 6 | |
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