SOLUTION: if a takes an old sweeper 30 hour to clean a street and takes a new and old sweepers together only 7.5 hours to clean the same street, then how long would it take for new sweeper

Question 734376: if a takes an old sweeper 30 hour to clean a street and takes a new and old sweepers together only 7.5 hours to clean the same street, then how long would it take for new sweeper to cleanse the same street?
Found 2 solutions by lynnlo, josmiceli:
Answer by lynnlo(4176) (Show Source): You can put this solution on YOUR website!

Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = time in hours for new sweeper to clean street
The new sweeper's rate of sweeping is ( 1 street cleaned ) / ( t hrs )
The old sweeper's rate of sweeping is ( 1 street cleaned / 30 hrs )
Together, their rate is ( 1 street cleaned ) / ( 7.5 hrs )
-------------
Add their rates of sweeping to get their rate sweeping together

Multiply both sides by

It will take the new sweeper 10 hrs to clean street
check:

OK

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