SOLUTION: One tractor can plow a field in 8 hours, and another in 10 hours. In how many hours can both tractors plow the field together ?

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Question 992470: One tractor can plow a field in 8 hours, and another in 10 hours. In how many hours can both tractors plow the field together ?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
1/x + 1/y = 1/z
1/8 + 1/10 = 1/z
5/40 + 4/40 = 1/z
9/40 = 1/z
9*z = 40*1
9z = 40
9z/9 = 40/9
z = 40/9 = 4.444 (approximate)

It will take approximately 4.444 hours to plow the field together.