A and B can complete a piece of work in 12 days and 18 days respective

1.	A and B can complete a piece of work in 12 days and 18 days respectively. They start working but 3 days before the completion of work, A left. In how many days will the total piece of work be completed?1. 9 days2. 6 days3. 7 days4. 5 days
Answer» Correct Answer - Option 1 : 9 days Given: A and B can complete a piece of work in 12 days and 18 days respectively. A left before 3 days from the completion of work. Concept used: Time = Work/Efficiency Calculation: A's 1 day work = 1/12 B's 1 day work = 1/18 (A and B)'s 1 day work = [(1/12) + (1/18)] ⇒ 5/36 As B alone worked for last 3 days, ⇒ B's 3 days work = 3/18 = 1/6 Remaining work = 1 – (1/6) = 5/6 Remaining work is done by A and B together. Time = Work/Efficiency ⇒ Time = (5/6) ÷ [(1/18) + (1/12)] ⇒ (5/6) ÷ (5/36) ⇒ 6 days. Total days taken by to complete aa piece of work = 6 days + 3 days ⇒ 9 days. ∴ A and B took 9 days to complete a piece of work.

A and B can complete a piece of work in 12 days and 18 days respectively. They start working but 3 days before the completion of work, A left. In how many days will the total piece of work be completed?1. 9 days2. 6 days3. 7 days4. 5 days

Answer» Correct Answer - Option 1 : 9 days

Given:

A and B can complete a piece of work in 12 days and 18 days respectively.

A left before 3 days from the completion of work.

Concept used:

Time = Work/Efficiency

Calculation:

A's 1 day work = 1/12

B's 1 day work = 1/18

(A and B)'s 1 day work = [(1/12) + (1/18)]

⇒ 5/36

As B alone worked for last 3 days,

⇒ B's 3 days work = 3/18 = 1/6

Remaining work = 1 – (1/6) = 5/6

Remaining work is done by A and B together.

Time = Work/Efficiency

⇒ Time = (5/6) ÷ [(1/18) + (1/12)]

⇒ (5/6) ÷ (5/36)

⇒ 6 days.

Total days taken by to complete aa piece of work = 6 days + 3 days

⇒ 9 days.

∴ A and B took 9 days to complete a piece of work.

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