question:10 books are placed at random in a shelf. The probability that a pair of books will always be together is?
Options:
(A) 1/6
(B) 1/7
(C) 1/5
(D) 1/9
(E) 1/2
answer:(C)
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


question:Which of the following numbers is divisible by 5?
Options:
(A) 3221
(B) 6175
(C) 6231
(D) 5813
(E) 4251
answer:(B)
Stream of consciousness:6175. This is the only option with last two digits divisible by 5


question:3 workers transfer a tool weighing 120kg in 12 seconds. How many men are required to transfer it in 9 seconds?
Options:
(A) 4
(B) 5
(C) 6
(D) 7
(E) 8
answer:
(A)
Stream of consciousness:We have, M1D1H1 = M2D2H2
3*120*12 = M2*120*9
M2 = 3*120*12/120*9 = 4