question:The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero?
Options:
(A) 7
(B) 4
(C) 12
(D) 19
(E) 28
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 and B can do a work in 18 days, B and C in 30 days and C and A in 36 days. In how many days will the work be completed, if all three of them work together?
Options:
(A) 360/13 days
(B) 350/13 days
(C) 160/13 days
(D) 260/13 days
(E) 960/13 days
answer:(A)
Stream of consciousness:One day work of A and B = 1/18
One day work of B and C = 1/30
One day work of C and A = 1/36
2(A + B + C) = 1/18 + 1/30 + 1/36
2(A + B + C) = 21/180
(A + B + C) = 13/360
Number of days required = 360/13 days.

question:A football field is 9600 square yards. If 1200 pounds of fertilizer are spread evenly across the entire field, how many pounds of fertilizer were spread over an area of the field totaling 5600 square yards?
Options:
(A) 450
(B) 600
(C) 700
(D) 2400
(E) 3200
answer:
(C)
Stream of consciousness:Answer C) 9600 yards need 1200 lbs
1 Yard will need 1200/9600 = 1/8 lbs
3600 Yards will need 1/8* 5600 Yards = 700lbs