Jennifer went on a run on Monday, Wednesday, and Friday. She averaged 6 miles per run. If she ran 2 miles on Monday and 4 miles on Friday, how many did she run on Wednesday?

Answer 1

This is kind of a reverse-average problem. In this instance, the average of three numbers is equal to 6.

In some other similar problems, you would be ashes to find the average of a given amount of numbers. You would add up those numbers, then divide the result by how many numbers you had. However in this case, you have two numbers and the average of three. Here’s how to find that third number:

Reverse the process: Start by multiplying the average by three (the number of different distances in each day):

6 * 3 = 18

Now SUBTRACT the numbers you have from the result:

18 - 4 - 2 = 12

So Friday’s run was 12 miles long.