SOLUTION: Please help me solve this! ** A farmer drives a tractor from one town to another town, a distance of 120 miles. He drives 10 miles per hour faster on the return trip, cutting 1 hou

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Question 30719: Please help me solve this! ** A farmer drives a tractor from one town to another town, a distance of 120 miles. He drives 10 miles per hour faster on the return trip, cutting 1 hour off the time. How fast does he drive each way?
Answer by Paul(988) About Me  (Show Source):
You can put this solution on YOUR website!
LEt the speed be x

Increased speed = x+10

Equation:



120[(x+10)-(x)]=(x)(x+10)







Use quadratic formula:

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+

a=1, b=10, c=-1200

x=%28-10%2B-sqrt%2810%5E2-4%2A1%2A-1200%29%29%2F%282%2A1%29

x=%28-10%2B-sqrt%284900%29%29%2F%282%2A1%29

x=%28-10-70%29%2F2  or x=%28-10%2B70%29%2F2

x=-40 or x=30

Remove the negative and simplfy the postive:

x=30

30+10=40

Hence, the speed going was 30mph and the speed returning was 40mph.

Paul.