q: An enterprising businessman earns an income of Re 5 on the first day of his business. On every subsequent day, he earns an income which is just thrice of that made on the previous day. On the 10th day of business, he earns an income of:
Options:
(A) 21
(B) 22
(C) 20
(D) 45
(E) 30
a: Stream of consciousness: 2nd day he earns = 3(2 5)
3rd day he earns = 3(3 5)
On 20th day he earns 3(20 -5) = 45 rupees The answer is (D).

question: A pipe can fill a cistern in 7 minutes whereas the cistern when fill can be emptied by a leak in 14 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 17
(B) 16
(C) 70
(D) 14
(E) 12
answer: Stream of consciousness: 1/7 - 1/14 = 1/14
14 minutes The answer is (D).

q: A train 280 m long, running with a speed of 63 km/hr will pass a tree in?
Options:
(A) 11
(B) 16
(C) 18
(D) 10
(E) 14
a: Stream of consciousness: Speed = 63 * 5/18 = 35/2 m/sec
Time taken = 280 * 2/35 = 16 sec The answer is (B).

question: 189. The inside dimensions of a rectangular wooden box
are 2 inches by 4 inches by 6 inches. A cylindrical
canister is to be placed inside the box so that it stands
upright when the closed box rests on one of its six
faces. Of all such canisters that could be used, what is
the radius, in inches, of the one that has maximum
volume?
Options:
(A) 2
(B) 4
(C) 5
(D) 6
(E) 8
answer: Stream of consciousness: Since the radius is squared, the biggest volume cylinder will have the biggest possible radius. To achieve that, let the smaller dimension of the rectangular box be the height. So, it will have 6x4 width x length. The biggest cylinder must fit both dimensions, so it must have at most a diameter of 4, so the radius will be 2. The answer is (A).

q: 10 books are placed at random in a shelf. The probability that a pair of books will always be together is ?
Options:
(A) 1/8
(B) 1/4
(C) 1/5
(D) 1/9
(E) 1/1
a: 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).

q: Three pipes A, B and C can fill a tank from empty to full in 30 minutes, 20 minutes and 10 minutes respectively. When the tank is empty, all the three pipes are opened. A, B and C discharge chemical solutions P, Q and R respectively. What is the proportion of solution R in the liquid in the tank after 3 minutes?
Options:
(A) 6/17
(B) 6/11
(C) 6/18
(D) 6/19
(E) 6/10
a:
Stream of consciousness: Part filled by (A + B + C) in 3 minutes = 3(1/30 + 1/20 + 1/10) = 11/20
Part filled by C in 3 minutes = 3/10
Required ratio = 3/10 * 20/11 = 6/11 The answer is (B).