How long would it take for them to complete the job if they were working together?

Question

A painter can finish painting a house in 3 hours. Her assistant takes 5 hours to finish the same job. How long would it take for them to complete the job if they were working together?

Answer 1

In one hour, the painter can complete 1/3rd of the house.

 

In one hour, the assistant can complete 1/5th of the house.

 

Together. they complete (1/3 + 1/5 = 8/15 of the house in one hour)

 

After hour 1, 8/15 of the house is complete.

 

All they need to complete the remaining part of the house is to paint 7/15ths of the house.

 

To find exact time, take 1 hour (60 minutes/8)= 7.5 minutes per part completed.

 

7.5 * 7 (# of parts remaining)= 52.5 minutes.

 

It should take them 1 hour and 52 minutes and 30 seconds.

Answer 2

Darinka,

 

You could probably set up a simultaneous and solve them. Or you take a simple approach: How long would it take them to finish painting 2 houses? 3 + 5 = 8 hours. One house, obviously is half the job and thus half the time. So, it takes 4 hours. I hope this helps.