Which one of the following is not a prime number?
Options:
(A) 51
(B) 61
(C) 71
(D) 82
(E) 91

91 is divisible by 7. So, it is not a prime number. So the answer is: (E).

3 friends A, B, C went for week end party to McDonald's restaurant and there they measure there weights in some order In 7 rounds. A, B, C, AB, BC, AC, ABC. Final round measure is 175kg then find the average weight of all the 7 rounds?
Options:
(A) 100 kgs
(B) 88.5 kgs
(C) 86.5 kgs
(D) 67.5 kgs
(E) 88.2 kgs

Average weight = [(a + b + c + (a+b) + (b+c) + (c+a)+(a+b+c)] / 7 = 4 (a+b+c) /7 = 4 x 175/7 = 100 kgs So the answer is: (A).

A and B are integers. The expression (A+1)(B+1) is even. What can be said about A and B?
Options:
(A) They are both even numbers.
(B) At least one of them is even
(C) At least one of them is odd.
(D) They are both odd.
(E) Nothing can be said surly on A and B

Odd x Odd = Odd
Odd x Even = Even
Even x Even = Even
To fulfill condition Either (A+1) or (B+1) needs to be Even
So either A or B needs to be odd
Or At Least one of them is odd. So the answer is: (C).

A man sells two articles for Rs.3600 each and he gains 30% on the first and loses 30% on the next. Find his total gain or loss?
Options:
(A) 9% loss
(B) 400
(C) 4000
(D) 324
(E) 200
(30*30)/100 = 9%loss So the answer is: (A).