A is 40% more efficient than B and C is 20% less efficient than B. Working together, they can finish a task in 15 days. In how many days, will B alone complete 75% of the task?

Answer: Option A

Solution

Answer: Option A

Solution:

$$\begin{array}{rl}& \left(7+5+4\right)\times 15\times \frac{75}{100}=\text{B}\times 5\\ & \text{B}=36\text{ days}\end{array}$$