Question

During the first four months of the year, Jack earned $1270, $1150, $870 and $1450 If Jack must have an average salary of at least $1150 in order to earn retirement benefits, what must Jack earn in the fifth month in order to qualify for benefits?

Answer 1

1010

Explanation:

There are a whole class of questions that rely on the method to this one.

First add up what you know

1270 + 1150 + 870 + 1450 = 4740

Now add on the 5th month (which you don't know. Call it x)

4740 + x

Divide by 5

(4740 + x)/5 = 1150 and that is your equation

Solution

Multiply both sides by 5

5*(4740 + x) / 5 = 1150 * 5

4740 + x = 5750

Subtract 4740 from both sides

4740 - 4740 + x = 5750 - 4740

x = 1010

Which seems kind of low, but that's what the numbers come to.