SOLUTION: It takes Jeff 90 mins. to mow the yard. It takes Joe 105 mins to mow the yard. What is the approximate time it will take if they work together to mow the yard? this is the p

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Question 723565: It takes Jeff 90 mins. to mow the yard. It takes Joe 105 mins to mow the yard. What is the approximate time it will take if they work together to mow the yard? this is the problem, how do I work it out? thanks
Found 3 solutions by checkley79, AnlytcPhil, Edwin McCravy:
Answer by checkley79(3341)   (Show Source): You can put this solution on YOUR website!
1/90+1/105=1/X FIND A COMMON DENOMINATOR FOR THE LEFT HAND FRACTIONS.
(105+90)/90*105=1/X
195/9,450-1/X CROSS MULTIPLY.
195X=9,450
X=9.450/195
X=48.46 MINS. ANS.
Answer by AnlytcPhil(1806)   (Show Source): You can put this solution on YOUR website!

Answer by Edwin McCravy(20054)   (Show Source): You can put this solution on YOUR website!
Here it is broken down so you can understand where everything comes from.

It takes Jeff 90 mins. to mow the yard. 
Therefore Jeff's mowing rate is 1 lawn per 90 minutes or  or

It takes Joe 105 mins to mow the yard.
Therefore Joe's mowing rate is 1 lawn per 105 minutes or  or

What is the approximate time it will take if they work together to mow the yard?
Let x be the answer, Then it takes them x mins to mow the yard working
together.
Therefore their combined mowing rate is 1 lawn per x minutes or  or  

The equation comes from:

                  

                      

                             

Solve that by multiplying through by 630x

Answer  minutes.


Edwin
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