Average of 20 numbers = 0
Sum of 20 numbers = (0 * 20) = 0
It is quite possible that 19 of these numbers may be positive and if their sum is a, then 20th number is (-a).
The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero?
Options:
(A) 87
(B) 15
(C) 17
(D) 19
(E) 16
(D)

I think answer on this one should be E too. Since we know that 14^7>19^4, as Will said one should always check if the number is positiv
What is the units digit of the expression 14^7−19^4?
Options:
(A)  0
(B)  3
(C)  4
(D)  6
(E)  8
(E)

(60/100) * 50 – (40/100) * 30
30 - 12 = 18

How much 60% of 50 is greater than 40% of 30?
Options:
(A) 18
(B) 55
(C) 33
(D) 22
(E) 11
(A)