Source: Revised GRE PDF 1st Ed. Section 5: Math; #23 (p. 79)

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The average (arithmetic mean) of the 11 numbers

The average (arithmetic mean) of the 11 numbers in a list is 14. If the average of 9 of the numbers in the list is 9, what is the average of the other 2 numbers?

1 Explanation

2

Gravatar Chris Lele, Magoosh Tutor

Sep 26, 2012 • Comment

Elizabeth Mendes

If you think more in terms of algebra, like me, I think there is an easier way to approach this problem. I also thought of how an average was found and how some value x and some value y make up the sum of the first average, and the sum of the group of 9, (x+y)/11=14. We are given another average that makes up the whole y/9=9. If you solve for y, you get 81. Plug in 81 to your original equation, you get 73, the sum of the other 2 numbers, and then all you are left to do is divide by 2 for 36.5

Aug 10, 2019 • Reply

David Recine, Magoosh Tutor

That is a great alternate approach with more of an algebra focus. :)

Aug 26, 2019 • Reply

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