A, B and C can do some work in 40 days. A and C together can do twice as much work as B alone. Find the time taken by B to do the whole work.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 120 days
Let the total work = 1 unit.
Given:
- $A + B + C = \frac{1}{40}$
- $A + C = 2B$
Step 1: Substitute $A + C$ in total work
$(A + C) + B = 2B + B = 3B$
So,
$3B = \frac{1}{40}$
Step 2: Find B’s rate
$B = \frac{1}{120}$
Step 3: Time taken by B alone
$\text{Time} = \frac{1}{B} = 120 \text{ days}$