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2006 SMT/General Problems/Problem 5

Problem

A geometric series is one where the ratio between each two consecutive terms is constant $(ex. 3, 6, 12, 24,\cdots)$. The fifth term of a geometric series is $5!$, and the sixth term is $6!$. What is the fourth term?

Solution

$5!:6!=1:6=20:5!$ So, the answer is $\boxed{20}$

See Also

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