Question

The time taken by A and B to complete a piece of work is 12 days and 8 days respectively. They start working together and B leaves the work after 4 days of starting. How many days will A take to complete the rest of the work? 
1. 1 day
2. 2 days
3. 2.5 days
4. 3 days
5. 5 days

Answer 1

Correct Answer - Option 2 : 2 days

Given:

A's time = 12 days

B's time = 8 days

B leaves after 4 days

Calculation:

Let total work be 24 (L.C.M of 12 and 8)

A's efficiency = 24/12 = 2 units/day

B's efficiency = 24/8 = 3 units/day

4 days work = (3 + 2) × 4 = 20 units

Remaining work = 4 units

required time = 4/2 = 2 days

∴ The answer is 2 days