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.

120 days

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

$\text{Time} = \frac{1}{B} = 120 \text{ days}$