SOLUTION: Make a table and solve. Gavin left early to drive to his parents' house and was able to drive 300 miles befor lunch. Due to increased traffic after lunch, his average speed for

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Question 1035360: Make a table and solve.
Gavin left early to drive to his parents' house and was able to drive 300 miles befor lunch. Due to increased traffic after lunch, his average speed for the ramaining 105 miles was 15 mi/hr less thn his average speed before lunch. If he drove for a total of 9 hr, determine his average speed before lunch and after lunch. What was his average sped for the trip?
Answer by jorel555(1290) About Me  (Show Source):
You can put this solution on YOUR website!
Let n equal his speed before lunch. Then:
300/n+105/n-15=9
300(n-15)+105n=9(n)(n-15)
300n+105n-4500=9n^2-135n
9n^2-540n+4500=0
n^2-60n+500=0
(n-50)(n-10)=0
n=50 or 10
The only reasonable answer is his speed before lunch was 50 mph, 35 mph after lunch!!!!!!!!!