SOLUTION: It takes my father 3 hours to plow our cornfield with his new tractor. Using the old tractor it takes me 5 hours. If we both plow for 1 hour before I go to school, how long will it

Question 489529: It takes my father 3 hours to plow our cornfield with his new tractor. Using the old tractor it takes me 5 hours. If we both plow for 1 hour before I go to school, how long will it take Dad to finish the plowing?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
It takes my father 3 hours to plow our cornfield with his new tractor.
Using the old tractor it takes me 5 hours.
If we both plow for 1 hour before I go to school, how long will it take Dad to finish the plowing?
:
let t = time it takes Dad to finish plowing
let the completed job = 1 (a plowed field)
:
+ = 1
Multiply by 15 to clear the denominators results:
3 + 5(5+1) = 15
3 + 5t + 5 = 15
5t = 15 - 8
5t = 7
t =
t = 1.4 hrs for Dad to finish
:
:
Check solution (Dad plowed for a total of 2.4 hrs)
1/5 + 2.4/3 =
.2 + .8 = 1; confirms our solution
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