Question 648820: Suppose a car drives on the freeway for 7 hours. In the first 3 hours, he travels at a constant
speed. For the remaining part of the trip, he travels 10 mph faster than during the rst part
of the drive. If he travelled 500 miles, how fast was he going during the rst part of the drive?
I just cant seem to come up with an equation, I need it explained. Any help would work thanks!
Answer by MathTherapy(10557)   (Show Source):
You can put this solution on YOUR website!
Suppose a car drives on the freeway for 7 hours. In the first 3 hours, he travels at a constant
speed. For the remaining part of the trip, he travels 10 mph faster than during the rst part
of the drive. If he travelled 500 miles, how fast was he going during the rst part of the drive?
I just cant seem to come up with an equation, I need it explained. Any help would work thanks!
Let speed during 1st part of trip be S
Then speed during last part of trip = S + 10
Distance covered during 1st part of trip, plus distance covered in last part of trip = total distance traveled, OR
3S + 4(S + 10) = 500
3S + 4S + 40 = 500
7S = 500 - 40
7S = 460
S, or speed during 1st part of trip =  , or  mph
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