SOLUTION: Mr. Castro drove 30 miles in the construction zone, and 120 miles on the highway. The total time for his trip was 3 hours, Find his speed on the highway if he was driving 30 mile

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Question 973125: Mr. Castro drove 30 miles in the construction zone, and 120 miles on the
highway. The total time for his trip was 3 hours, Find his speed on the
highway if he was driving 30 miles per hour faster on the highway.
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
Mr. Castro drove 30 miles in the construction zone, and 120 miles on the
highway. The total time for his trip was 3 hours, Find his speed on the
highway if he was driving 30 miles per hour faster on the highway.
***
let x=Mr. Castro's speed in the construction zone
x+30=Mr. Castro's speed on the highway
travel time=distance/speed
..
30%2Fx%2B120%2F%28x%2B30%29=3
lcd:x(x+30)
30(x+30)+120x=3x(x+30)
30x+900+120x=3x^2+90x
3x^2-60x-900=0
x^2-20x-300=0
(x+10)(x-30)=0
x=30
x+30=60
Mr. Castro's speed on the highway=60 mph