question:There are 7 fictions and 6 non-fictions. How many cases are there such that 2 fictions and 2 non-fictions are selected from them?
Options:
(A) 90
(B) 120
(C) 315
(D) 180
(E) 200
answer:(C)
Stream of consciousness:Number of ways of selecting 2 fiction books = 7C2
Number of ways of selecting 2 non fiction books = 6C2
7C2 * 6C2 = 21 * 15 = 315

question:A train running at the speed of 60 km/hr crosses a pole in 9 seconds. Find the length of the train?
Options:
(A) 150
(B) 8827
(C) 166
(D) 199
(E) 121
answer:(A)
Stream of consciousness:Speed = 60*(5/18) m/sec = 50/3 m/sec
Length of Train (Distance) = Speed * Time
(50/3) * 9 = 150 meter

question:A train 300 m long is running at a speed of 99 km/hr. In what time will it pass a bridge 195 m long?
Options:
(A) 17
(B) 18
(C) 19
(D) 20
(E) 21
answer:
(B)
Stream of consciousness:Speed = 99 * 5/18 = 55/2 m/sec
Total distance covered = 300 + 195 = 495 m
Required time = 495 * 2/55 = 18 sec