Question

The mean of four numbers is 7. Three of the numbers are 2, 5, and 17. What is the fourth number?

YOU MUST Show your work.

Answer 1

If the mean of four numbers is 7, we know that their sum is 7 * 4 = 28. We can use this information to find the last number. If the fourth number is x, we can write:

2 + 5 + 17 + x = 28

24 + x = 28

x = 4