question: A pipe can fill a cistern in 18 minutes whereas the cistern when fill can be emptied by a leak in 20 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 17
(B) 180
(C) 70
(D) 120
(E) 12
answer: Stream of consciousness: 1/18 - 1/20 = 1/180
180 minutes The answer is (B).

q: A can do a piece of work in 3 hours; B and C together can do it in 2 hours, which A and C together can do it in 2 hours. How long will B alone take to do it?
Options:
(A) 6hours
(B) 3hours
(C) 2hours
(D) 5hours
(E) 4hours
a: Stream of consciousness: A's 1 hour work = 1/3;
(B + C)'s 1 hour work = 1/2;
(A + C)'s 1 hour work = 1/2
(A + B + C)'s 1 hour work = (1/3 + 1/2) = 5/6
B's 1 hour work = (5/6 - 1/2) = 1/3
B alone will take 3 hours to do the work. The answer is (B).

question: Find the average of the first 23 natural numbers?
Options:
(A) 8
(B) 9
(C) 10
(D) 11
(E) 12
answer: Stream of consciousness: Average of the first 'n' natural numbers = (n + 1)/2
We get (23 + 1)/2 = 12 The answer is (E).

q: A bullet train 140 m long is running at 60 kmph. In how much time will it pass a platform 310 m long?
Options:
(A) 34 Seconds
(B) 22 Seconds
(C) 41 Seconds
(D) 24 Seconds
(E) 27 Seconds
a: Stream of consciousness: 27 Seconds
Distance travelled = 140 + 310m = 450m
Speed = 60 * 5/8 = 50/3m
Time = 450 * 3/50 = 27 Seconds The answer is (E).

question: Rs.800 amounts to Rs.920 in 3 years at simple interest. If the interest is increased by 3%, it would amount to how much?
Options:
(A) 288
(B) 277
(C) 209
(D) 992
(E) 612
answer: Stream of consciousness: (800*3*3)/100 = 72
920 + 72 = 992 The answer is (D).

question: What approximate value should come in place of question mark (?) in the following equation
287.532 + 1894.029 757.48 = 443.095 + ?
Options:
(A) 870
(B) 790
(C) 680
(D) 770
(E) 890
answer:
Stream of consciousness: ? = 285 + 1895 755 745 or, ? = 680 The answer is (C).