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2006 AIME I Problems/Problem 2

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Problem

Let set \mathcal{A} be a 90-element subset of \{1,2,3,\ldots,100\}, and let S be the sum of the elements of \mathcal{A}. Find the number of possible values of S.

Solution

The smallest S is 1+2+ \ldots +90 = 91 \cdot 45 = 4095. The largest S is 11+12+ \ldots +100=111\cdot 45=4995. All numbers between 4095 and 4995 are possible values of S, so the number of possible values of S is 4995-4095+1=901.

See also

2006 AIME I (ProblemsResources)
Preceded by
Problem 1
Followed by
Problem 3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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