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2005 PMWC Problems/Problem I6

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Problem

A group of 100 people consists of men, women and children (at least one of each). Exactly 200 apples are distributed in such a way that each man gets 6 apples, each woman gets 4 apples and each child gets 1 apple. In how many possible ways can this be done?

Solution

m + w + c = 100 6m + 4w + c = 200

Subtracting the second equation from the first, we get 5a + 3b = 100. Looking at this equation \mod{5}, we see that 3b must be a multiple of 5, so 5|b. Thus the choices for b are 5,10,15,20,25,30, which gives us 6 possible choices.

See also

2005 PMWC (Problems)
Preceded by
Problem I5
Followed by
Problem I7
I: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
T: 1 2 3 4 5 6 7 8 9 10
Want to learn how to tackle those tough MATHCOUNTS and AMC counting and probability problems? Check out Art of Problem Solving's Introduction to Counting & Probability by David Patrick.
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