Question

A can do a piece of work in 12 days. B can do this work in 16 days. A started the work alone. After how many days should b join him, so that the work is finished in 9 days?

Answer 1

A and B can do a piece of work in 12 days and 16 days respectively. A started the work and B joined A after some days, and the total work was completed in 9 days. After how many days did B join A?

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5 ANSWERS



Anonymous

Answered Jun 10, 2018

The easiest way to understand rate problems like this is to define the amount of work that needs to be done and the rate at which each worker works.

1 unit of work is required to be completed.

A can complete 1 unit of work in 12 days, therefore A produces 1/12 unit per day.

B can complete 1 unit of work in 16 days, therefore B produces 1/16 unit per day.

The total 1 unit was completed in 9 days. We know that A worked the entire time and that B worked an unknown amount of time.

A contributed 9/12 units of work in 9 days. Therefore B must have completed the remaining 3/12 units. The amount of time it would take B to complete this amount of work is calculated as 3/12 divided by 1/16, which is equal to 4.

The final answer is that A worked for 9 days and B worked for 4 days. Therefore, B joined A after 5 days (on the 6th day of work).