2022 AMC 12A Problem 10
Problem 10 of 25EasierCounting & Probability
What is the number of ways the numbers from to can be split into pairs such that for each pair, the greater number is at least times the smaller number?
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Solution
Any number or larger cannot be a smaller element (its double exceeds ), so – are all larger elements and – are all smaller elements.
Match each smaller to a larger Processing from the most restrictive: forces ( way); then has left (); has has has has has
The number of matchings is
Thus, the correct answer is E.