Question

A can do a piece of work in 7 days of 9 hours each and b can do it in 6 days of 7 bours each. How long will they take to do it, working together 8 hours a day?

Answer 1

Answer:

Step-by-step explanation:

Trick here is to first calculate the amount of work done per hour :

In one hour

A can do 1/(7*9) of the work, and

B can do 1/(6*7) of the work.

Add to get the amount of work done per hour when they both work together:

1/(7*9) + 1/(6*7) = 15/378

Since they work 8 hours each day,

In one day they can finish 8*(15/378) of the work which equals 20/63

That means they finish (20/63) th of the work in 1 day.

To get the number of days it takes to finish the entire work, simply reverse the ratio:  63/20 = 3.15 days for the work to be completed