q: Pipes A and B can fill a cistern in 8 and 24 minutes respectively. They are opened an alternate minutes. Find how many minutes, the cistern shall be full?
Options:
(A) 22
(B) 12
(C) 88
(D) 99
(E) 27
a: Stream of consciousness: 1/8 + 1/24 = 1/6
6 * 2 = 12 The answer is (B).

question: Find the invalid no.from the following series 13, 18, 25, 30, 37, 40
Options:
(A) 23
(B) 26
(C) 40
(D) 42
(E) 49
answer: Stream of consciousness: The differences between two successive terms from the beginning are 7, 5, 7, 5, 7, 5. So, 40 is wrong. The answer is (C).

q: What amount does Kiran get if he invests Rs. 16000 at 15% p.a. simple interest for four years?
Options:
(A) Rs. 25800
(B) Rs. 15600
(C) Rs. 21600
(D) Rs. 24800
(E) Rs. 25600
a: Stream of consciousness: Simple interest = (16000 * 4 * 15)/100 = Rs. 9600
Amount = P + I = 16000 + 9600 = Rs. 25600 The answer is (E).

question: The length of a rectangle is increased by 25% and its breadth is decreased by 20%. What is the effect on its area?
Options:
(A) 10000
(B) 18999
(C) 16990
(D) 16007
(E) 16991
answer: Stream of consciousness: 100 * 100 = 10000
125 * 80 = 10000 The answer is (A).

q: If six persons sit in a row, then the probability that three particular persons are always together is?
Options:
(A) 1/6
(B) 1/3
(C) 1/5
(D) 1/1
(E) 1/2
a: Stream of consciousness: Six persons can be arranged in a row in 6! ways. Treat the three persons to sit together as one unit then there four persons and they can be arranged in 4! ways. Again three persons can be arranged among them selves in 3! ways. Favourable outcomes = 3!4! Required probability = 3!4!/6! = 1/5 The answer is (C).

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 40 minutes. How long will it take to fill the cistern if all the three are opened at the same time?
Options:
(A) 17 1/9
(B) 17 1/3
(C) 17 1/7
(D) 17 1/9
(E) 17 1/1
a:
Stream of consciousness: 1/20 + 1/30 - 1/40 = 7/120
120/7 = 17 1/7 The answer is (C).