question: The speed of a train is 90 kmph. What is the distance covered by it in 12 minutes?
Options:
(A) 15
(B) 18
(C) 77
(D) 52
(E) 42
answer: Stream of consciousness: 90 * 12/60 = 18 kmph The answer is (B).

q: In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Options:
(A) 6
(B) 7
(C) 8
(D) 9
(E) 5
a: Stream of consciousness: Speed in still water = 1 (11 + 5)/2 kmph = 8 kmph. The answer is (C).

question: In what time will a railway train 20 m long moving at the rate of 36 kmph pass a telegraph post on its way?
Options:
(A) 5 sec
(B) 4 sec
(C) 3 sec
(D) 6 sec
(E) 2 sec
answer: Stream of consciousness: T = 20/36 * 18/5 = 2 sec The answer is (E).

q: Two pipes A and B can fill a cistern in 20 and 30 minutes respectively, and a third pipe C can empty it in 50 minutes. How long will it take to fill the cistern if all the three are opened at the same time?
Options:
(A) 17 1/4 min
(B) 28 1/7 min
(C) 17 1/7 min
(D) 17 1/8 min
(E) 15 15/19 min
a: Stream of consciousness: 1/20 + 1/30 - 1/50 = 19/300
300/19 = 15 15/19 The answer is (E).

question: What is the sum of the 1st 5 prime numbers greater than 20?
Options:
(A) 121
(B) 151
(C) 168
(D) 164
(E) 161
answer: Stream of consciousness: Required sum = (23 + 29 + 31 + 37 + 41) = 161
Note: 1 is not a prime number The answer is (E).

question: 10 books are placed at random in a shelf. The probability that a pair of books will always be together is?
Options:
(A) 1/6
(B) 1/7
(C) 1/5
(D) 1/9
(E) 1/2
answer:
Stream of consciousness: 10 books can be rearranged in 10! ways consider the two books taken as a pair then number of favourable ways of getting these two books together is 9! 2!
Required probability = 1/5 The answer is (C).