SOLUTION: Working together, two sisters can do the yard work at their house in 48 minutes. When the older girl does it all herself, she can complete the job in 20 minutes less time than it t
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Question 600379: Working together, two sisters can do the yard work at their house in 48 minutes. When the older girl does it all herself, she can complete the job in 20 minutes less time than it takes the younger girl working all alone. How long does it take the older girl to do the yard work?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Working together, their rate of working is:
( 1 yard ) / ( 48 min )
Let = time in minutes for
younger girl to finish yard work
---------
( 1 yard ) / ( t min ) = younger girls rate
of working
( 1 yard ) / ( t - 20 min ) = older girl's rate
of working
----------
Add their individual rates of working to get
their rate working together
Multiply both sides by
Use quadratic formula
too fast- faster than both working together
min
It takes the older girl 1 hr and 27 min working alone
check:
OK
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