Use some thinking to answer the following question. The average of five numbers is 9. The average of first two numbers is 7 and the average of last two numbers is 12. What is the middle number?
Options:
(A) 7
(B) 8
(C) 5
(D) 10
(E) 6
The total of five numbers = 5x9 = 45
The total of first 2 and last 2 numbers is = 2 X 7+2 X 12 = 38
So, the middle number is (45 - 38 ) = 7 So the final answer is (A).