Q: A Train requires 10 seconds to pass a pole while it requires 40 seconds to cross a stationary train which is 300 mtrs long. Find the speed of the train.
Options:
(A) 36kmph
(B) 42kmph
(C) 48kmph
(D) 52kmph
(E) 64kmph
A: OK... Stream of consciousness: In 10s the train crosses the pole and in 40 sec the train crosses one more stationary train
In 30 sec the train travels a distance of 300 mtrs
Speed = 300/30 = 10 m/s = 10 * 18/5 = 36 kmph
The answer is (A).

Q: In what time will a railway train 65 m long moving at the rate of 32 kmph pass a telegraph post on its way?
Options:
(A) 3 sec
(B) 4 sec
(C) 5 sec
(D) 6 sec
(E) 7 sec
A: OK... Stream of consciousness: T = 65/32 * 18/5 = 7 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: OK... Stream of consciousness: 1/20 + 1/30 - 1/50 = 19/300
300/19 = 15 15/19
The answer is (E).

Q: A and B can do a work in 10 days and 15 days respectively. A starts the work and B joins him after 5 days. In how many days can they complete the remaining work?
Options:
(A) 6 days
(B) 2 days
(C) 8 days
(D) 4 days
(E) 3 days
A:
OK... Stream of consciousness: Work done by A in 5 days = 5/10 = 1/2
Remaining work = 1/2
Work done by both A and B in one day = 1/10 + 1/15 = 5/30 = 1/6
Remaining work = 1/2 * 6/1 = 3 days.
The answer is (E).