The mean of three numbers x, y and z is 6 and the mean of five numbers x, y, z, a and b is 8. Find the mean of a and b.

11

Step-by-step explanation:

To find the mean of a set of numbers, we add all of the numbers together and divide the sum by the size of the set. For that first set, we have three numbers, x, y and z, so the equation for their mean would be

We can rearrange this equation by multiplying both sides by 3, getting the equivalent equation

Let's do the same thing for the second mean:

With the two equations we've obtained, we can subtract (1) from (2) to get rid of x, y, and z, leaving us with

To find the mean of a and b now, all we have to do is divide both sides of the equation by 2, and we see that

16

step-by-step explanation:

2 x 40 = 80

80/5

= 16