Question

A and B can do a piece of work in 15 days and C and D can do same piece of work in 18 days. In how many days will A, B, C and D do the same piece of work together?
1. 90/11 days
2. 45/11 days
3. 135/11 days
4. 60/11 days

Answer 1

Correct Answer - Option 1 : 90/11 days

Given:

A and B can do a piece of work in 15 days.

C and D can do the same piece of work in 18 days.

Concept Used:

Efficiency is inversely proportional to the time taken to complete the work.

Calculation:

In 1 day, part of work done by A and B = 1/15.

In 1 day, part of work done by C and D = 1/18.

In 1 day, part of work done by A and B and C and D together = 1/15 + 1/18

⇒ (6 + 5)/90

⇒ 11/90

According to the concept used, time taken by A and B and C and D together to complete the work will be 90/11 days.

∴ A and B and C and D together will complete the work in 90/11 days.