GRE Sample Test 4 Quantitative Reasoning 2

Question : 16 of 20

Marks: +1, -0

If the average of two numbers is 3y and one of the numbers is y − z, what is the other number, in terms of y and z?

y + z
3y + z
4y - z
5y - z
5y + z

Solution:

The average is

{\The \sum \of \terms}/{\The \number \of \terms}

. Here you have y − z and the other number, which you can call x. The average of x and y − z is 3y, so 3y =

{x+y-z}/2

.
Multiplying both sides by 2 gives 6y = x + y − z. Subtracting y − z from both sides gives 5y + z = x. So the other number, x, is 5y + z, answer choice (E).

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