Question

The average age of three people running for election is 42. A fourth person joins the race and the average drops to 40. What is the fourth person's age?​

Answer 1

Call the four people
`abc` and
`d`.

We know:

`(a+b+c)/(3)`
`=42`

and

`(a+b+c+d)/(4)`
`=40`

Thus:

`a + b + c = 126`

`(126+4)/(4) = 40`

`126 + d =160`

`d = 34`