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2006 Alabama ARML TST Problems/Problem 2

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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
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15
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