Question

The mean of 15 numbers is 12. An extra number is included and the mean increases to 13. What the extra number?

Answer 1

Answer: 28

Explanation:

The mean of 15 numbers = 12

Then , the sum of the numbers = 12x15 = 180

Let the extra number included be
`x` , then

The new sum =
`x + 180`

And the new total number will increase from 15 to 16

new mean = 13 , so we have :

`(x+180)/(16) = 13`

`x+ 180 = 16(13)`

`x + 180 = 208`

`x = 208 - 180`

`x = 28`

therefore , the extra number is 28