Average problem 1 by Dhaval Furia

Algebra Level pending

The average of 30 30 integers is 5 5 . Among these 30 30 integers, there are exactly 20 20 which do not exceed 5 5 . What is the highest possible value of the average of these 20 20 integers?

3.5 5 4.5 4

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1 solution

Dhaval Furia
May 14, 2020

In order to maximize the average of the 20 integers, we need to maximize their sum, which can be done by minimizing the sum of the other 10 (out of 30) integers which do exceed 5

That is possible when those 10 are 6 each, making their average 6

Now a simple application of alligation reveals that the average of the first 20 integers is 4.5

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