Question

Ind 59:

Your Mom can clean your entire house in 3 hours. However,
your dad takes 5
hours to clean the house. Determine how long it will take for them to clean the
house if they work together.

Answer 1

It takes them 1.875 hours.

Explanation:

Here, the job is cleaning the house.

Mom does 1 job in 3 hours.

In 1 hour, mom does 1/3 of the job.

Dad does 1 job in 5 hours.

In 1 hour, dad does 1/5 of the job.

Mom and dad working together do the job in x hours.

In 1 hour, mom and dad together do 1/x of the job.

1/3 + 1/5 = 1/x

5/15 + 3/15 = 1/x

8/15 = 1/x

8x = 15

x = 15/8 = 1.875

Answer: It takes them 1.875 hours.