q: A man rows his boat 85 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?
Options:
(A) 5 kmph
(B) 6 kmph
(C) 7 kmph
(D) 8 kmph
(E) 9 kmph
a: OK... Speed downstream = d/t = 85/(2 1/2) = 34 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (34 - 18)/2 = 8 kmph
The answer is (D).

q: he population of a city is 120,000. If it increases at the rate of 6% per annum, then what will be its population 2 years hence?
Options:
(A) 137787
(B) 134832
(C) 139776
(D) 139728
(E) 139718
a: OK... Population after n years = P [1 + (R/100)]2
Population after 2 years = 120000 * [1 + 6/100]2 = (120000 x 53/50 x 53/50) = 134832
The answer is (B).

q: Find the invalid no.from the following series 13, 18, 25, 30, 37, 40
Options:
(A) 13
(B) 18
(C) 40
(D) 37
(E) 25
a:
OK... The differences between two successive terms from the beginning are 7, 5, 7, 5, 7, 5. So, 40 is wrong.
The answer is (C).