# Using combinatorics identities

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• June 7th 2010, 08:04 AM
oldguynewstudent
Using combinatorics identities
Again just to make sure I understand what I'm doing:

What is the sum of the numbers in row 15 (i.e. n=15) of Pascal's triangle?
(Answer this without computing row 15.)

$2^n = \sum_{k=0}^{n}\left({n\atop k}\right)$ for all n >= 0.

So the answer would be $2^{15}$ correct?
• June 7th 2010, 08:12 AM
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Quote:

Originally Posted by oldguynewstudent
Again just to make sure I understand what I'm doing:

What is the sum of the numbers in row 15 (i.e. n=15) of Pascal's triangle?
(Answer this without computing row 15.)

$2^n = \sum_{k=0}^{n}\left({n\atop k}\right)$ for all n >= 0.

So the answer would be $2^{15}$ correct?

Correct! And don't forget the first row is row 0.