1.

A and B can complete a piece of work in 18 days and 45 days respectively, they start work together but B left after some time and A finish the remaining work in 4 days, After how many days from the start B did leave the work?1. 12 days2. 10 days3. 9 days4. 14 days5. None of these

Answer» Correct Answer - Option 2 : 10 days

Given:

A alone can complete work = 18 days

B alone can complete work = 45 days

A and B start working together but B left after some time and A finish the remaining work in 4 days

Concept:

Total work = Time × Efficiency

Calculation:

Work done by

Time taken

(in day)

Efficiency

A

18

90/18 = 5

B

45

90/45 = 2

Total work = L. C. M. = 90

 

Start work together but B left after some time and A finish the remaining work in 4 days

Last 4 days work done by A = 4 × 5 = 20 unit

Work for did together = 90 – 20 = 70 unit

Efficiency of A and B = 5 + 2 = 7 unit

Let, After x days from the start B did leave the work

Then, x = 70/7 = 10 days

∴ After 10 days from the start B did leave the work

 

 



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