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jmc

algebra senior

Problem

Two numbers are independently selected from the set of positive integers less than or equal to 5. What is the probability that the sum of the two numbers is greater than their product? Express your answer as a common fraction.
Solution
Let's name the two numbers and We want the probability that , or (applying Simon's Favorite Factoring Trick). This inequality is satisfied if and only if or When , can equal through , and when and can equal through . There are ways to choose and so the probability is
Final answer
\frac{9}{25}