question:The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero?
Options:
(A) 18
(B) 16
(C) 17
(D) 19
(E) 13
answer:(D)
Stream of consciousness: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).


question:A man rows his boat 75 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?
Options:
(A) 1 kmph
(B) 6 kmph
(C) 5 kmph
(D) 8 kmph
(E) 7 kmph
answer:(B)
Stream of consciousness:Speed downstream = d/t = 75/(2 1/2) = 30 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (30 - 18)/2 = 6 kmph


question: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%
answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
(B)
Stream of consciousness:P = (P*3*R)/100
R = 33 1/3%