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

Algebra ->  Rate-of-work-word-problems -> 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      Log On


   

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) About Me  (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%2F5 + %28t%2B1%29%2F3 = 1
Multiply by 15 to clear the denominators results:
3 + 5(5+1) = 15
3 + 5t + 5 = 15
5t = 15 - 8
5t = 7
t = 7%2F5
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