q: The smallest prime number is:
Options:
(A) 1
(B) 2
(C) 3
(D) 4
(E) 5
a: OK... The smallest prime number is 2.
The answer is (B).

q: 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
a: OK... Number of ways of selecting 2 fiction books = 7C2
Number of ways of selecting 2 non fiction books = 6C2
7C2 * 6C2 = 21 * 15 = 315
The answer is (C).

q: A teacher has to choose the maximum different groups of three students from a total of six students. Of these groups, in how many groups there will be included in a particular student?
Options:
(A) 6
(B) 8
(C) 10
(D) 12
(E) 15
a:
OK... If students are A, B, C, D, E and F; we can have 6C3 groups in all. However, if we have to count groups in which a particular student (say A) is always selected we would get 5C2 = 10 ways of doing it.
The answer is (C).