MathCastle
Counting & ProbabilitySuperchallengeDistributions: Stars & Bars and Integer Solutions

Distributions: Stars & Bars and Integer Solutions · Superchallenge problem

How many ordered quadruples (a,b,c,d)(a,b,c,d) of nonnegative integers satisfy a+b+c+d=15a+b+c+d=15, if none of a,b,c,da,b,c,d may equal 22 and none may equal 55?