q: A pipe can fill a cistern in 20 minutes whereas the cistern when fill can be emptied by a leak in 28 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 76 minutes
(B) 29 minutes
(C) 70 minutes
(D) 17 minutes
(E) 98 minutes
a: Stream of consciousness: 1/20 - 1/28 = 1/70
70 minutes The answer is (C).

question: At 15:00 there were 21 students in the computer lab. At 15:03 and every three minutes after that, 3 students entered the lab. If at 15:10 and every ten minutes after that 8 students left the lab, how many students were in the computer lab at 15:44 ?
Options:
(A) 7
(B) 14
(C) 25
(D) 27
(E) 30
answer: Stream of consciousness: Initial no of students + 3 * (1 + No of possible 3 minute intervals between 15:03 and 15:44) -
8 *(1 + No of possible 10 minute intervals between 15:10 and 15:44)
20 + 3*14 -8 * 4 = 27 The answer is (D).

q: The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up tails?
Options:
(A) 1/8
(B) 1/2
(C) 3/4
(D) 7/8
(E) 15/16
a: Stream of consciousness: P(at last 1 tails) = 1 - P(all heads) = 1 - (1/2)^3 = 7/8. The answer is (D).

question: A committee has 5 men and 6 women. What are the number of ways of selecting a group of eight persons?
Options:
(A) 165
(B) 185
(C) 205
(D) 225
(E) 245
answer: Stream of consciousness: Total number of persons in the committee = 5 + 6 = 11
Number of ways of selecting group of eight persons = C = C = (11 * 10 * 9)/(3 * 2) = 165 ways. The answer is (A).

q: A man took loan from a bank at the rate of 12% p.a. S.I. After 3 years he had to pay Rs. 5400 interest only for the period. The principal amount borrowed by him was?
Options:
(A) 3887
(B) 2768
(C) 15000
(D) 76887
(E) 16711
a: Stream of consciousness: Principal = (100 * 5400) / (12 * 3) = Rs. 15000 The answer is (C).

q: A train 360 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 190 m long?
Options:
(A) 40 sec
(B) 42 sec
(C) 44 sec
(D) 48 sec
(E) 50 sec
a:
Stream of consciousness: Speed = 45 * 5/18 = 25/2 m/sec
Total distance covered = 360 + 190 = 550 m
Required time = 550 * 2/25 = 44 se The answer is (C).