Time and Work - General Aptitude

Q1:

A takes twice as much time as B or thrice as much time as C to finish a piece of work. Working together, they can finish the work in 2 days. B can do the work alone in:

A 4 days

B 6 days

C 8 days

D 12 days

ANS:B - 6 days

Suppose A, B and C take x, x and x days respectively to finish the work.
2 3
Then, 1 + 2 + 3 = 1
x x x 2
6 = 1
x 2
 x = 12. So, B takes (12/2) = 6 days to finish the work.