Question: A train 420 m long, running with a speed of 63 km/hr will pass a tree in?
Options:
(A) 36 sec
(B) 16 sec
(C) 17 sec
(D) 88 sec
(E) 12 sec
Answer: Speed = 63 * 5/18 = 35/2 m/sec
Time taken = 420 * 2/35 = 36 sec
The answer is (A).

Question: If the ratio of boys to girls in a class is B and the ratio of girls to boys is G; then 5 (B + G) is ?
Options:
(A) Equal to 3
(B) Less than 3
(C) More than 3
(D) Less than 1/3
(E) none of these
Answer: Let number of boys = x
Let number of girls = y
Therefore x/y = B and y/x = G
5(B + G) = 5[(x/y) + (y/x)] = 5[(x2 + y2)/xy] > 5
The answer is (E).

Question: The speed of a boat in still water is 60kmph and the speed of the current is 30kmph. Find the speed downstream and upstream?
Options:
(A) kmph
(B) kmph
(C) kmph
(D) kmph
(E) kmph
Answer: Speed downstream = 60 + 30 = 90 kmph
Speed upstream = 60 - 30 = 30 kmph
The answer is (D).

Question: How many two-digit numbers satisfy this property.: The last digit (unit's digit) of the square of the two-digit number is 3 ?
Options:
(A) 4
(B) 0
(C) 3
(D) 2
(E) 1
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
A number ending with 3 can never be a perfect square.
The answer is (B).