Q: The average of 13 numbers is 58. Average of the first 7 of them is 57 and that of the last 7 is 61. Find the 8th number?
Options:
(A) 72
(B) 83
(C) 45
(D) 53
(E) 64 Let's give some random thoughts before answering.
Sum of all the 13 numbers = 13 * 58 = 754
Sum of the first 7 of them = 7 * 57 = 399
Sum of the last 7 of them = 7 * 61 = 427
So, the 8th number = 427 + 399 - 754 = 72.
Therefore, the answer is (A).