Question

Given a set `{-1, x ,-4, -21}`, for what x would the mean of the set be 0?

Answer 1

`x=26`

Explanation:

It is assumed that by Mean we mean Arithmetic Mean. This is just a sum of all numbers divided by 'number' of numbers. As there are four numbers here,for mean to be `0`, sum of four numbers needs to be `0` too.

As sum of three known numbers is -26, `x` must be equal to `26` for mean to be `0`.