Page 115 - NUMINO Challenge_D2

13 Work and Its Efficiency

Basic Concepts Work and Its Efficiency

Let 1 represents the total amount of work. If it takes days for A to finish this

work alone and days for B to finish this work alone, the amount of work

that A can do in a day is 1 1 , and the amount of work that B can do in a

day is 1 1.

If A and B work together, the amount of work that they can do is 1 1.
Therefore, it takes 1 ( 1 1 ) days for them to finish the work.

Example It takes 60 days for John to finish the amount of work that Thomas
can finish in 30 days. How many days does it take for John and
Thomas to finish this work?

Class Notes

Let 1 represents the total amount of work. Since it takes 30 days for Thomas to finish the

work, the amount of work he can do in a day is 1 .

Since it takes 60 days for John to finish the work, the amount of work he can do in a

day is 1 .

If they work together, the amount of work they can do in a day is .

Therefore, it takes 1 (days) for them to finish the work.

Try It Again It takes 10 hours for A and 40 hours for B to fix the road. How
many hours does it take to fix the road if A and B work
together?

112 NUMINO Challenge D2