Question

A can complete a work in 9 days and B can complete the same work in 12 days. They start working together, but due to some reason A left the work 5 days before the completion of work. then find in how many days the whole work is completed?
1. 5 days
2. 7 days
3. 8 days
4. 9 days

Answer 1

Correct Answer - Option 3 : 8 days

Given:

A can complete a work in 9 days

B can complete a work in 12 days

A left the work before 5 days of completion of the work

Formula Used:

Work = Efficiency × Time

Calculation:

Let the whole work be completed in D days 

Total work = LCM of 9, 12

⇒ 36 

Efficiency of A = 36/9

⇒ 4

Efficiency of B = 36/12

⇒ 3

B worked for D days, while A worked for (D – 5) days 

4(D – 5) + 3 × D = 36

⇒ 4D – 20 + 3D = 36

⇒ 7D = 56

⇒ D = 8 

∴ The whole work is completed in 8 days