Rationale: D = 100 + 170 = 270
S = 36 * 5/18 = 10 mps
T = 270/10 = 27 sec
The answer: (E)
Question: How many seconds will a train 100 meters long take to cross a bridge 170 meters long if the speed of the train is 36 kmph?
Options:
(A) 54 sec
(B) 65 sec
(C) 25 sec
(D) 45 sec
(E) 27 sec

Rationale: Sum of all the 13 numbers = 13 * 60 = 780
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 - 780 = 46.
The answer: (A)
Question: The average of 13 numbers is 60. Average of the first 7 of them is 57 and that of the last 7 is 61. Find the 8th number?
Options:
(A) 43
(B) 30
(C) 35
(D) 45
(E) 50

Rationale: P = (P*30*R)/100
R = 3 1/3%
The answer: (A)
Question: At what rate percent on simple interest will a sum of money double itself in 30 years?
Options:
(A) 3 1/3%
(B) 3 1/6%
(C) 3 1/5%
(D) 3 5/3%
(E) 7 1/3%