document.write( "Question 156779: Jack usually mows his lawn in 5 hours. Mary can mow the same yard in 7 hours. how much time would it take for them to mow the lawn together?\r
\n" ); document.write( "\n" ); document.write( "they could mow the lawn in ???? hours if worked together. \n" ); document.write( "

Algebra.Com's Answer #115597 by phd(3) $\"\"$ $\"About$

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Consider Jack's rate as $\"1%2F5\"$ lawn per hour and Mary's rate as $\"1%2F7\"$ lawn per hour. Together they have a rate of $\"1%2F5+%2B+1%2F7+=+12%2F35\"$ . Thus in one hour they can mow $\"12%2F35\"$ of the lawn. Now the rate times the time it takes them will give you one whole lawn. So, since they are mowing just one lawn take the reciprocal of $\"12%2F35\"$ which is $\"35%2F12\"$ and this is how many hours it takes them to mow a lawn together. Now this might be easier to see in minutes. If we divided 35 by 12 we get 2 with 11 left over. So $\"+2+%2811%2F12%29\"$ hours. Thinking of a clock which has 12 numbers. The 11 on a clock represents 55 minutes. Another way of looking at that is that $\"11%2F12+=+55%2F60\"$ and there are 60 minutes in one hour. Therefore the answer is 2 hours and 55 minutes which is less time than it take either of them alone. \n" ); document.write( "

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