[Ques]: 10 books are placed at random in a shelf. The probability that a pair of books will always be together is
Options:
(A) 1/9
(B) 1/7
(C) 1/5
(D) 1/1
(E) 1/2
*Ans*: (C)
--CoT--: 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

[Ques]: In what time a sum of money double itself at 3% per annum simple interest?
Options:
(A) 33 1/9%
(B) 33 1/3%
(C) 332 1/3%
(D) 33 9/3%
(E) 13 1/3%
*Ans*: (B)
--CoT--: P = (P*3*R)/100
R = 33 1/3%

[Ques]: Find the invalid no.from the following series 13, 18, 25, 30, 37, 40
Options:
(A) 23
(B) 25
(C) 40
(D) 46
(E) 48
*Ans*: (C)
--CoT--: The differences between two successive terms from the beginning are 7, 5, 7, 5, 7, 5. So, 40 is wrong.

[Ques]: What is theleast number should be added to 1056, so the sum of the number is completely divisible by 23?
Options:
(A) 1
(B) 2
(C) 4
(D) 5
(E) 6
*Ans*: (B)
--CoT--: (1056 / 23) gives remainder 21
21 + 2 = 23, So we need to add 2