SOLUTION: Harry drove for 6 hours on the freeway, then decreased his speed by 20 miles per hour and drove for 5 more hours on a country road. If his total trip was 637 miles then what was hi

Algebra ->  Angles -> SOLUTION: Harry drove for 6 hours on the freeway, then decreased his speed by 20 miles per hour and drove for 5 more hours on a country road. If his total trip was 637 miles then what was hi      Log On


   



Question 851321: Harry drove for 6 hours on the freeway, then decreased his speed by 20 miles per hour and drove for 5 more hours on a country road. If his total trip was 637 miles then what was his speed on the freeway?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +d+ = distance driven on the freeway in miles
Let +s+ = Harry's speed on freeway in mi/hr
+637+-+d+ = distance driven on country road
+s+-+20+ = Harry's speed on country road
-------------------
Equation for freeway:
(1) +d+=+s%2A6+
Equation for country road:
(2) +637+-+d+=+%28+s+-+20+%29%2A5+
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Substitute (1) into (2)
(2) +637+-+6s+=+%28+s+-+20+%29%2A5+
(2) +637+-+6s+=+5s+-+100+
(2) +11s+=+737+
(2) +s+=+67+
Harry's speed on freeway was 67 mi/hr
check:
(1) +d+=+s%2A6+
(1) +d+=+67%2A6+
(1) +d+=+402+
and
(2) +637+-+d+=+%28+67+-+20+%29%2A5+
(2) +637+-+d+=+47%2A5+
(2) +d+=+637+-+235+
(2) +d+=+402+
OK