Marge drove by 66 miles per hour on the interstate
Step-by-step explanation:
Marge drive 290 miles in five hours, her trip has two stages
- She drove 3 hours on the interstate
- The remainder of the trip was on a road that caused her to reduce her speed by 20 mph
We need to find how fast Marge drove on the interstate
Assume that she drove by speed x miles per hour on interstate
∵ Distance = speed × time
∵ Her speed on the interstate is x mph
∵ The time of interstate is 3 hours
∴ The distance of interstate = x × 3 = 3x miles
∵ The time of the total trip is 5 hours
∵ She spent 3 hours on the interstate
∴ The time of the remainder of the trip = 5 - 3 = 2 hours
∵ She reduced her speed 20 mph for the remainder of the trip
∴ Her speed on the remainder of the trip = x - 20 mph
∴ The remainder distance = (x - 20) × 2
∴ The remainder distance = 2x - 40 miles
∵ The total distance of the trip is 290 miles
- Equate the sum of the two distances above by 290
∴ 3x + 2x - 40 = 290
- Add the like terms in the left hand side
∴ 5x - 40 = 290
- Add 40 to both sides
∴ 5x = 330
- Divide both sides by 5
∴ x = 66
Marge drove by 66 miles per hour on the interstate
Learn more:
You can learn more about speed, time and distance in brainly.com/question/9998060
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