Question 274937
Mary can paint a house in 4 hrs.John can paint the same house in 6 hrs. How long will it take to paint house together.  First I converted hours to minutes, added them together, then divided by two. please help me set up this problem correctly.
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Instead of converting to minutes, you could have added 4 hours and 6 hours = 10 hours.  It still wouldn't be right.
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Mary paints 1/4 of the hours per hour.
John paints 1/6 per hour.
Add those up --> 1/4 + 1/6 = 5/12 per hour
--> 12/5 hours to do the job = 2.4 hours
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Use the shortcut, product/sum
4*6/(4+6) = 24/10 = 2.4 hours