q: X can finish a work in 18 days. Y can finish the same work in 15 days. Yworked for 5 days and left the job. how many days does X alone need to finish the remaining work?
Options:
(A) 12
(B) 5
(C) 6
(D) 8
(E) 9
a: OK... Work done by X in 1 day = 1/18
Work done by Y in 1 day = 1/15
Work done by Y in 5 days = 5/15 = 1/3
Remaining work = 1 – 1/3 = 2/3
Number of days in which X can finish the remaining work = (2/3) / (1/18) = 12
The answer is (A).

q: Eight friends go to watch a movie but only 5 tickets were available. In how many different ways can 5 people sit and watch the movie?
Options:
(A) 8C5
(B) 8*7*6*5*4
(C) 5!
(D) 8!/5!
(E) 8*5
a: OK... Choosing 5 out of 8, when order matters P58, or choosing 5 out of 8, without order and then arranging: C58∗5!
The answer is (B).

q: In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Options:
(A) 3 km/hr
(B) 2 km/hr
(C) 4 km/hr
(D) 6 km/hr
(E) 8 km/hr
a:

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
OK... Speed in still water = 1/2 (11 + 5) kmph = 8 kmph.
The answer is (E).