Question: Calculate the speed of a boat in still water (in km/hr) if in one hour, the boat goes 15 km/hr downstream and 7 km/hr upstream.
Options:
(A) 12 kmph
(B) 13 kmph
(C) 14 kmph
(D) 15 kmph
(E) 11 kmph
Answer: Speed in still water = (15 + 7)1/2 kmph = 11 kmph.
The answer is (E).

Question: K-numbers are positive integers with only 2's as their digits. For example, 2, 22, and 222 are K-numbers. The K-weight of a number n is the minimum number of K-numbers that must be added together to equal n. For example, the K-weight of 50 is 5, because 50 = 22 + 22 + 2 + 2 + 2. What is the K-weight of 750?
Options:
(A) 10
(B) 11
(C) 12
(D) 13
(E) 15
Answer: 750 = 3*222 + (22*3) + 9*2
K weight of 600 = 3 +3+9 = 15
The answer is (E).

Question: There are 42 distinct numbers in set M, there are 28 distinct numbers in set N, and there are 12 distinct numbers that are in both sets M and N. Set H is the set containing the elements that are in at least one of sets M and N. How many elements are in set H?
Options:
(A) 39
(B) 40
(C) 51
(D) 58
(E) 63
Answer: {Total} = {M} + {N} - {Both}
{Total} = 42 + 28 - 12 = 58.
The answer is (D).

Question: A train running at the speed of 60 km/hr crosses a pole in 3 sec. What is the length of the train?
Options:
(A) 56
(B) 78
(C) 27
(D) 79
(E) 50
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
Speed = 60 * 5/18 = 50/3 m/sec
Length of the train = speed * time = 50/3 * 3 = 50 m
The answer is (E).