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March 29, 2015

March 29, 2015

Posted by **Laura** on Saturday, October 18, 2008 at 11:43am.

Jack mows the lawn in 4 hours, mary mows the lawn in 5 hours. how long will it take them if they mowed the lawn together?

I have a hard time figuring out which formula to use to solve a problem in a word problem can anyone help and tell me how to set up the problem so I can do the math?

- Algebra -
**Deanna**, Saturday, October 18, 2008 at 12:02pmHello Laura,

the method that i would recommend is this simple method (assuming that both of them mow the lawn at a constant speed):

Jack->4h can complete lawn

jack->1h can complete 1/4 lawn

Mary->5h can complete lawn

Mary->1h can complete 1/5 lawn

Together->1h can complete 1/4+1/5=9/20 lawn.

That means that in 1 hour they can complete 9/20 lawn. To figure out time just take 20/20 divide by 9/20, the answer is 2/2/9. Hope that helps ^_^. Of course don't forget to put it in hours! ^_^

- Algebra -
**drwls**, Saturday, October 18, 2008 at 1:35pmThe combined rate of lawn mowing is 9/20 lawn/hour. To mow one lawn therefore takes 20/9 hour, or 2 and 2/9 hours.

Deanna's answer was correct but the 2/2/9 at the end was mistyped.

- Algebra -
**Deanna**, Sunday, October 19, 2008 at 1:00amHello Drwls,

sorry, but i don't understand what you mean by the 2/2/9 at the end was mistyped? Thank you for correcting my mistake if i had made one though! ^_^

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