Question: The average mark obtained by 22 candidates in an examination is 45. The average of the first ten is 55 while the last eleven is 40 .The marks obtained by the 11th candidate is ?
Options:
(A) 2
(B) 0
(C) 9
(D) 8
(E) 6
Answer: It is clear that 22 x 45 = 10 x 55 + K + 11 x 40 K = 0
The answer is (B).

Question: A bullet train 140 m long is running at 60 kmph. In how much time will it pass a platform 360 m long?
Options:
(A) 30 Seconds
(B) 22 Seconds
(C) 41 Seconds
(D) 24 Seconds
(E) 29 Seconds
Answer: 30 Seconds
Distance travelled = 140 + 360m = 500m
Speed = 60 * 5/8 = 50/3m
Time = 500 * 3/50 = 30 Seconds
The answer is (A).

Question: Find the mean proportional between 49 & 64?
Options:
(A) A) 59
(B) B) 61
(C) C) 56
(D) D) 65
(E) E) 67
Answer: Formula = ab
A = 49 and B = 64
4964 = 7 8 = 56
The answer is (C).

Question: The average of 13 numbers is 60. Average of the first 6 of them is 57 and that of the last 8 is 61. Find the 8th number?
Options:
(A) 46
(B) 48
(C) 50
(D) 52
(E) 54
Answer:
Sum of all the 13 numbers = 13 * 60 = 780
Sum of the first 6 of them = 6 * 57 = 342
Sum of the last 8 of them = 8 * 61 = 488
So, the 8th number = 342 + 488 - 780 = 50.
The answer is (C).