A can complete a piece of work in 10 days and B can complete it in 20

1.	A can complete a piece of work in 10 days and B can complete it in 20 days. A starts working and B works on every alternate day. In how many days total work will be completed if B left 5 days before the completion of work?1. 6 days2. 9 days3. 5 days4. 8 days
Answer» Correct Answer - Option 2 : 9 days Given: A can complete a piece of work in 10 days and B can complete it in 20 days. A starts working and B works on every alternate day. Before 5 days of the completion of work, B left the work. Concepts used: Efficiency = Work/Time Calculation: A can complete a piece of work in 10 days and B can complete it in 20 days. Efficiency = Work/Time 1-day work of A = 1/10 1-day work of B = 1/20 1 day work of A and B = 1/10 + 1/20 = 3/20 A and B started working together but before 5 days of the completion of work, B left the work. 5 days work of A = 5/10 = 1/2 Remaining work = 1 – (1/2) = 1/2 A and B work together on every alternate day. 2 days work of A and B = 1-day work of A + 1-day work of A and B ⇒ 1/10 + 3/20 ⇒ 5/20 = 1/4 1/4 work is done by A and B in 2 days. ⇒ 1 full piece of work is done by A and B in 8 days. ⇒ 1/2 work is done by A and B in 4 days. Total time taken to complete work = 5 days + 4 days = 9 days. ∴ A and B complete piece of work in 9 days if B assists A on every alternate day and if B left work before 5 days of completion of work.

A can complete a piece of work in 10 days and B can complete it in 20 days. A starts working and B works on every alternate day. In how many days total work will be completed if B left 5 days before the completion of work?1. 6 days2. 9 days3. 5 days4. 8 days

Answer» Correct Answer - Option 2 : 9 days

Given:

A can complete a piece of work in 10 days and B can complete it in 20 days.

A starts working and B works on every alternate day.

Before 5 days of the completion of work, B left the work.

Concepts used:

Efficiency = Work/Time

Calculation:

A can complete a piece of work in 10 days and B can complete it in 20 days.

Efficiency = Work/Time

1-day work of A = 1/10

1-day work of B = 1/20

1 day work of A and B = 1/10 + 1/20 = 3/20

A and B started working together but before 5 days of the completion of work, B left the work.

5 days work of A = 5/10 = 1/2

Remaining work = 1 – (1/2) = 1/2

A and B work together on every alternate day.

2 days work of A and B = 1-day work of A + 1-day work of A and B

⇒ 1/10 + 3/20

⇒ 5/20 = 1/4

1/4 work is done by A and B in 2 days.

⇒ 1 full piece of work is done by A and B in 8 days.

⇒ 1/2 work is done by A and B in 4 days.

Total time taken to complete work = 5 days + 4 days = 9 days.

∴ A and B complete piece of work in 9 days if B assists A on every alternate day and if B left work before 5 days of completion of work.