question:Which one of the following is not a prime number?
Options:
(A) 2
(B) 3
(C) 5
(D) 9
(E) 7
answer:(D)
Stream of consciousness:9 is divisible by 3. So, it is not a prime number.

question:A 70 cm long wire is to be cut into two pieces so that one piece will be 2/5th of the other, how many centimeters will the shorter piece be?
Options:
(A) 21
(B) 20
(C) 17
(D) 12
(E) 18
answer:(B)
Stream of consciousness:1: 2/5 = 5: 2
2/7 * 70 = 20

question:The speed of a boat in still water is 50kmph and the speed of the current is 20kmph. Find the speed downstream and upstream?
Options:
(A) 40, 68 kmph
(B) 40, 30 kmph
(C) 70, 30 kmph
(D) 40, 60 kmph
(E) 20, 60 kmph
answer:
(C)
Stream of consciousness:Speed downstream = 50 + 20 = 70 kmph
Speed upstream = 50 - 20 = 30 kmph