7 Sam can shovel his driveway in 2 hours His little brother Max would take 3 hours if he worked alone How long would it take the two of them to do the job if they worked together?

Answer 1

2.5hrs :)

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Should be :( since that is the WRONG answer - as a simple credibility check on the answer would tell you. If they work together, how can it take longer than Sam doing it alone?

Sam can do the driveway in 2 hours so Sam does 1/2 driveways per hour.

Max can do the driveway in 3 hours so Max does 1/3 driveways per hour.

So Sam + Max do 1/2 + 1/3 = 5/6 driveways per hour.

To do 1 driveway would, therefore, take them 1/(5/6) = 6/5 hours = 1.2 hours or 1 hour 24 mintes.