Question

80, 80, 84, 85, 88, 92, 97, 98

The average (arithmetic mean) of the 8 numbers listed
above is 88. Of the following, which pair of numbers
could be removed from the list without changing the
average?

(A) 80 and 97
(B) 80 and 98
(C) 84 and 92
(D) 84 and 97
(E) 85 and 92

Answer 1

c

Answer 2

come on, you can do this, take the sum of everything and divide by 8

Answer 3

What you need to think about is that the two numbers should be equally bigger & smaller than the arithmetic mean if you want it to remain constant.
Since the mean is 88 then:
Option A: 80 is -8 from the mean and 97 is +9 = Mean will not remain constant
Option B: -8 and +10
Option C: -4 and +4
Option D: -4 and +9
Option E: -3 and +4

From this you see that only option C would not change the mean.