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9 votes
9 votes
if the set s consists of five consecutive positive integers, what is the sum of these five integers? the integer 11 is in s, but 10 is not in s. the sum of the even integers in s is 26.

User Jrochkind
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1 Answer

15 votes
15 votes

Answer:

sum = 65

Explanation:

You want the sum of the set of 5 consecutive positive integers such that the sum of the even integers in the set is 26.

Solution

The sum of even integers will be a multiple of 3 if the middle integer of the set is even. Here, that sum is 26, not a multiple of 3. Hence the middle integer of the set is 26/2 = 13, and the sum of the set is 13·5 = 65.

The sum of the five integers is 65.

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Additional comment

When working "consecutive integer" problems, it is often useful to think in terms of the average of the integers, the middle one of an odd-length set, or the number halfway between the two middle ones of an even-length set.

A set of 5 integers will have either 3 odds and 2 evens, or 3 evens and 2 odds. The set here obviously does not have 3 even integers (whose sum would be 3 times the middle one).

The set is s = {11, 12, 13, 14, 15}. 10 is not in the set, but 11 is. The sum of evens is 12+14=26.

User Matthew Vincent
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