A problem by Asher Joy

Level pending

How many non-negative integer triplets (a,b,c) are there, such that a+b+c = 9?


The answer is 55.

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1 solution

Asher Joy
Dec 25, 2013

We can use the stars and banners (a.k.a Balls and Urns) quick-trick. Getting 2 banners and 9 stars. So we get an answer of (9+2)C(9) which is equal to 55.

http://en.wikipedia.org/wiki/Stars and bars_(combinatorics) When I try to explain it with asterisks and / it doesn't work. Sorry!

Asher Joy - 7 years, 4 months ago

would you please explain the solution more extendedly, thanks in advance

Don Vito - 7 years, 4 months ago

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