2006 Alabama ARML TST Problems/Problem 2

Problem

Compute $\sum_{k=1}^{5}\sum_{n=1}^{6}kn$.

Solution

For each value of k, the sum is equal to $1k+2k+3k+4k+5k+6k=21k$.

$\sum_{k=1}^{5}21k=21*15=\boxed{315}$

See also

2006 Alabama ARML TST (Problems)
Preceded by:
Problem 1
Followed by:
Problem 3
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