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'A' can do a work in 20 days and 'B' can do the same work in 15 days. 'B' works for 6 days and leaves work. In how many days can 'A' alone complete the remaining work? A. 12 days B. 4 days C. 6 days D. 5 days

'A' can do a work in 20 days and 'B' can do the same work in 15 days. 'B' works for 6 days and leaves work. In how many days can 'A' alone complete the remaining work? A. 12 days B. 4 days C. 6 days D. 5 days Correct Answer A

Given:

A can complete a work in 20 days.

B can complete a work in 15 days

Concept Used:

Total units of work is equal to the LCM of number of days required to complete the work.

Efficiency = Total units of work/Number of days taken

Calculation:

Total units of work, LCM of 20 and 15

Total units of work,

⇒ 60 units

Efficiency of A,

⇒ 60/20

⇒ 3 units/day

Efficiency of B,

 ⇒ 60/15

⇒ 4 units/day

B worked for 6 days and left,

Total units of work completed by B in 6 days,

⇒ 6 × 4

⇒ 24 units

Remaining units of work completed by A,

⇒ Remaining units of work = 60 – 24

⇒ Remaining units of work = 36 units

Time taken to complete the work,

⇒ 36/3

⇒ 12 days

∴ A can complete the remaining work in 12 days

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