‘A’ takes twice as much time ‘B’ to complete a work and ‘C’ does it in the same time as both ‘A’ and ‘B’ together do it. if all three of them work together and complete the work in 5 days, then the time taken by ‘B’ to complete the work alone is:

Correct option is C

Work done = time × efficiency
A,B and C takes x, x/2, and x/3 days respectively to finish the work.
According to question

6x=1/5
x = 6 × 5
x = 30
Time taken by B = 30/2 = 15 days.