The average of nine numbers is 17. The average of first four numbers is 20 and the average of last four numbers is 16. What is the middle number?
Options:
(A) A) 7
(B) B) 8
(C) C) 9
(D) D) 10
(E) E) 11 OK. Let's think. Some random thoughts first:
The total of nine numbers = 9X17 = 153
The total of first 4 and last 4 numbers is = 4 X 20+4 X 16 = 144
So, the middle number is (153 - 144 ) = 9 The answer: (C).