Homework Help: pre calc

Posted by kayla on Thursday, September 25, 2008 at 7:05pm.

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.

I got 2.5 hours but i think that is totally wrong?????

pre calc - bobpursley, Thursday, September 25, 2008 at 7:18pm
combined rate=field/3hrs + field/5hrs

time=field/(field/3 + field/5)
time= 15/(8)= less than your time.

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