A and B can do a piece of work in 20 days. B and C together can do it in 40 days. If A is thrice as good a workman as C, find in how many days B alone can do the work?
Answer & explanation
Correct answer: option 2
A : C = 3 : 1
Make total work equal
(A + B) × 20 = (B + C) × 40
A + B = 2B + 2C
A - 2C = B
3 - 2 × 1 = B ⇒ B = 1
Total work = ( 3 + 1 ) × 20 = 80
Time taken by B = \(\frac{80}{1}\) = 80 days