SOLUTION: After a heavy snowfall, Brian can shovel the entire driveway in 30 minutes. If his brother Alan helps, the job takes only 20 minutes. How long would it take Alan to do the job by

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Question 615267: After a heavy snowfall, Brian can shovel the entire driveway in 30 minutes. If his brother Alan helps, the job takes only 20 minutes. How long would it take Alan to do the job by himself?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You must add their rates of working to get
their rate working together
Brian's rate: ( 1 driveway ) / ( 30 min )
Brian's rate + Alan's rate: ( 1 driveway ) / ( 20 min )
Let Alan's rate working alone = ( 1 driveway / x min )
-------------
+1%2F30+%2B+1%2Fx+=+1%2F20+
Multiply both sides by +60x+
+2x+%2B+60+=+3x+
+x+=+60+
Alan can do the job alone in 1 hour