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# Stars and Bars with Restriction

I just encountered the stars and bars technique page on Brilliant. https://brilliant.org/assessment/techniques-trainer/stars-and-bars/

The example problem asks How many ordered sets of non-negative integers are there such that $$a + b + c + d = 10$$

I was wondering, If an upper limit is placed on one or two of the variables, for example if $$a<5$$ and $$b<4$$, then how will the solution change?

Note by Sameer Jain
3 years, 11 months ago

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Okay brother the solution is simple First find the no of solutions without any restriction Now you have to subtract 3 cases, Case 1 When a =5 then the solve b+c+d=5; Case 2 When b=4; Case 3 When both a and b are at their maximas.; Subtract these cases from your solution. PS- case 3 is not valid in this case.

- 3 years, 8 months ago