q: From the set of numbers x, y, t, z, p, q, r and w, how many different combinations can we have without the t,p,q and r in them? Ex:. (x,y), (x), (w,z,y,x), etc and (x,y)=(y,x)
Options:
(A) 10
(B) 12
(C) 15
(D) 16
(E) 30
a: OK... Another way: Any letter (x, y, z, w) can be included or not. So, we have 2^4 combinations - 4 empty combination = 12 combinations
The answer is (B).

q: If the given two numbers are respectively 7% and 28% of a third number, then what percentage is the first of the second ?
Options:
(A) 20%
(B) 25%
(C) 18%
(D) 30%
(E) none of these
a: OK... Here, l = 7 and m = 28
Therefore, first number = l/m x 100% of second number = 7/28 x 100% of second number = 25% of second number
The answer is (B).

q: How much 60% of 50 is greater than 30% of 30?
Options:
(A) 21
(B) 91
(C) 11
(D) 17
(E) 12
a:
OK... (60/100) * 50 (30/100) * 30
30 - 9 = 21
The answer is (A).