q: X can finish a work in 15 days. Y can finish the same work in 20 days. Y worked for 12 days and left the job. how many days does X alone need to finish the remaining work?
Options:
(A) 5
(B) 3
(C) 4
(D) 7
(E) 8
a: OK... Work done by X in 1 day = 1/15
Work done by Y in 1 day = 1/20
Work done by Y in 12 days = 12/20 = 3/5
Remaining work = 1 3/5 = 2/5
Number of days in which X can finish the remaining work = (1/3) / (1/15) = 5
The answer is (A).

q: A can do a piece of work in 20 days. B in 15 days A and C in 12 days. In how many days can A finish the work if he is assisted by B on one day and C on the next, alternately?
Options:
(A) 2 days
(B) 8 days
(C) 6 days
(D) 8 days
(E) 9 days
a: OK... A + B = 1/20 + 1/15 = 7/60
A + C = 1/20 + 1/12 = 8/60
7/60 + 8/60 = 15/60 = 1/4
4 days * 2 = 8 days
The answer is (B).

q: What is the next number of the following sequence.
8, 8, 6, 2,.... ?
Options:
(A) -4
(B) -5
(C) -6
(D) -7
(E) -8
a:
OK... 8-(2*0) = 8
8-(2*1) = 6
6-(2*2) = 2
2-(2*3) = -4
The answer is (A).