Question

The mean of 4 numbers is 15. 3 of the numbers are 18, 14 and 12. What is the other number?

Answer 1

Answer:

Call the numbers a, b, c, d. What does it say if their mean is 15? That would be that added together then divided by 4 you get 15. So the number before you divided by 4, which is the sum, was 60. If you know some algebra, the equation (a+b+c+d)/4=15 gives the sum of 60 when you multiply both sides