If the average of 10 numbers is 10 and the sum of five of the numbers is -25 what is the average of the other 5 numbers?
sum of all 10 numbers is 100
sum of one set of 5 numbers is -25
so the sum of the other set of 5 numbers must be 125
(125 + (-25) = 100 )
and the average of that second set of 5 numbers must be 125/5 or 25