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2014 AMC 10A Question 8

AMC10 · 2014 AMC 10A

Question 8

Which of the following numbers is a perfect square?
  1. $\dfrac{14!15!}2$
  2. $\dfrac{15!16!}2$
  3. $\dfrac{16!17!}2$
  4. $\dfrac{17!18!}2$
  5. $\dfrac{18!19!}2$