Question

Tom can do a job in 4 hours while Sam can do it in 6 hours. How many hours would it take to complete this job if they work together?

Answer 1

12/5hours=2.4 hours

Explanation:

Sam:6hours

Tom:4hours

This is a rate problem

Sam's rate is one job completed in 6 hours which is 1/6

Tom's rate is one job completed in 4 hours which is 1/4

Together, they could complete 1/4+1/6 of the job in y hours

We are trying to find the rate at which Sam and Tom could complete the job together, or one job in x days, for a rate of 1/y

1/4+1/6=1/y

The least common denominator is 12y

Multiplying through by the LCD which gives:

12y(1/4)+ 12y (1/6)= 12y (1/y)

3y + 2y=12

5y = 12

y=12/5 hours=2.4hours

Therefore it will take 12/5 hours or 2.4 hours to complete the job if they work together