question:Ravi can do a piece of work in 50 days while Prakash can do it in 75 days. In how many days will they finish it together?
Options:
(A) 30 days
(B) 35 days
(C) 25 days
(D) 27 days
(E) 29 days
answer:(A)
Stream of consciousness:1/50 + 1/75 = 5/150
30/1 = 30 days

question:The no. of girls in a class are seven times the no. of boys, which value cannever be the of total students?
Options:
(A) 3
(B) 5
(C) 8
(D) 9
(E) 11
answer:(C)
Stream of consciousness:Let the boys are X, then girls are 7X, total = X+7X = 8X
So it should be multiple of 8, 30 is not a multiple of 8.

question:The ratio of males and females in a city is 7 : 8 and the percentage of children among males and females is 25% and 20% respectively. If the number of adult females in the city is 156800 what is the total population?
Options:
(A) 245000
(B) 367500
(C) 196000
(D) 171500
(E) None of these
answer:
(B)
Stream of consciousness:Number of females = 156800 10080 = 196000
\ Number of males = 78 196000 = 171500
\ Total population = 196000 + 171500 = 367500