SOLUTION: Bret drove for 4hrs on the freeway, then decreased his speed by 20mph and drove for 5more hours on a country road. If his total trip was 485miles, then what was his speed on the fr

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Question 504099: Bret drove for 4hrs on the freeway, then decreased his speed by 20mph and drove for 5more hours on a country road. If his total trip was 485miles, then what was his speed on the freeway?
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
f = freeway speed
c = country road speed
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4f + 5c = 485 miles
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f = c+20
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substitute
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4(c+20) +5c = 485
4c +80 + 5c = 485
9c +80 = 485
9c = 405
c = 45 mph
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f = 45+20
f = 65 mph
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Always check your work.
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4f = 4(65) = 260 miles
5c = 5(45) = 225 miles
260+225 = 485 miles
Correct.
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Re-read the question to make sure you answer it.
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What was his speed on the freeway? 65 mph.
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Done.