A, B and C can all together do a piece of work in 10 days, in which B takes 3 times as long as A and C together to do the work. In how many days can B alone do the work?

A. 50 days

B. 40 days

C. 10 days

D. 15 days

Answer: Option B

Solution(By Examveda Team)

\[\begin{array}{*{20}{c}} {}&{\left( {A + C} \right)}&:&B \\ {{\text{Time}}}&1&{}&3 \\ {{\text{Efficiency}}}&3&{}&1 \end{array}\]
$$B\,{\text{alone}} = \frac{{10 \times 4}}{1} = 40\,{\text{days}}$$