Laura can pick up her toys in 5 minutes. Her mother can pick up the toys in 2 minutes.

Question

how long will it take laura and her mother to pick up the toys together?

Answer 1

Hi Cate--think of it this way:

 

Laura can pick up 1/5 of the toys in 1 minute, mom can pick up 1/2 of the toys in one minute.

 

Together, in one minute they can pick up 1/5 + 1/2, or 2/10 + 5/10, which is 7/10 of the toys.

 

So, that means they can pick up ONE tenth of the toys in 1/7th of a minute, or 60/7 seconds, or 8.5 seconds.

 

Multiply that by 10 (for 10/10 of the toys) and you get

 

8.5 seconds x 10 = 85 seconds, or 1 minute 25 seconds.

 

Wow! Can they do my kitchen next?!?

 

Hope this helps.

 

Matt in New York