SOLUTION: Jack mowes the lawn in 4hrs and mary mowes the lawn in 7 hours. How long would it take them to both mow the yard?

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Question 281633: Jack mowes the lawn in 4hrs and mary mowes the lawn in 7 hours. How long would it take them to both mow the yard?
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
1/4+1/7=1/X
(7+4)/4*7=1/X
11/28=1/X CROSS MULTIPLY
11X=28
X=28/11
X=2.5454 HOURS WORKING TOGETHER.