SOLUTION: How far can a person drive into the country at the average rate of 30MPH and return over the same road at the average rate of 20 MPH if the person travels a total of 5 hours?

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Question 992951: How far can a person drive into the country at the average rate of 30MPH and return over the same road at the average rate of 20 MPH if the person travels a total of 5 hours?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +t+ = time in hrs for 1st part of trip
(1) +d+=+30t+
(2) +d+=+20%2A%28+5+-+t+%29+
Substitute (1) into (2)
(2) +30t+=+20%2A%28+5-t+%29+
(2) +30t+=+100+-+20t+
(2) +50t+=+100+
(2) +t+=+2+
and
(1) +d+=+30%2A2+
(1) +d+=+60+
The person can drive 60 mi into country
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check:
(2) +d+=+20%2A%28+5+-2+%29+
(2) +d+=+20%2A3+
(2) +d+=+60+
OK