SOLUTION: IT WOULD TAKE BETSEY 4 HOURS TO CLEAN HER ROOM. HER MOM COULD DO IT IN 2 HOURS. USE ALGEBRA TO FIND HOW LONG IT WOULD TAKE THEM WORKING TOGETHER?

Question 387082: IT WOULD TAKE BETSEY 4 HOURS TO CLEAN HER ROOM. HER MOM COULD DO IT IN 2 HOURS. USE ALGEBRA TO FIND HOW LONG IT WOULD TAKE THEM WORKING TOGETHER?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Think of these problems as adding their
rates of working separately
Let = Betsy's rate of working alone
Let = Mother's rate of working alone
Let = their rate of working together
---------------------------
The rule is:

given:

This means 1 room cleaned in 4 hours

This means 1 room cleaned in 2 hours
----------------
So far I've got

I can express as , or 1 room
cleaned in hours
Now I have:

Multiply both sides by

hours
This is the same as:
min, or 1 hour and 20 minutes working together
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