SOLUTION: A towns old street sweeper can clean the streets in 60 hrs. Working together with a new sweeper they can do the job in 15 hrs. How long would it take the new sweeper to do the job

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A towns old street sweeper can clean the streets in 60 hrs. Working together with a new sweeper they can do the job in 15 hrs. How long would it take the new sweeper to do the job      Log On


   

Question 1065360: A towns old street sweeper can clean the streets in 60 hrs. Working together with a new sweeper they can do the job in 15 hrs. How long would it take the new sweeper to do the job working alone?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Old sweeper's rate:
[ 1 job ] / [ 60 hrs ]
New sweeper's rate:
[ 1 job ] / [ t hrs ]
Their rate working together:
[ 1 job ] / [ 15 hrs ]
---------------------------
Add their rates of working to get
their rate working together
+1%2F60+%2B+1%2Ft+=+1%2F15+
Multiply both sides by +60t+
+t+%2B+60+=+4t+
+3t+=+60+
+t+=+20+
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The new sweeper does the job in 20 hrs
working alone
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check:
+1%2F60+%2B+1%2F20+=+1%2F15+
Multiply both sides by +60+
+1+%2B+3+=+4+
+4+=+4+
OK