Question 411522
A farmer can plow a field in 12 hours by using one tractor. His son, using a different tractor can plow it in 10.5 hours. How long will it take the farmer and his son working together to plow the field?
Sol'n:
rate x time = 1

1/12+1/10.5 = 1/x
1/x = 5/28
x = 28/5
x = 5.6 days ----answer

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