Question

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 one hour before I go to school, how long will it take him to finish the plowing?

Answer 1

It takes my Father 3 hours to plow the 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 him to finish

:

let t = time Dad plows after he goes to school

:

Let the completed job = 1; (a plowed field)

:

A shared work equation

%28%28t%2B1%29%29%2F3 + 1%2F5 = 1

Multiply by 15, results

5(t+1) + 3 = 15

5t + 5 + 3 = 15

5t = 15 - 8

t = 7%2F5

ANSWER

t = 1.4 hrs or 1 + .4(60) = 1 hr 24 more minutes to finish

hope this helps :)