A ramp with a constant incline is made to connect a driveway to a front door. At a point 4 feet from the driveway, the height of the ramp is 12 inches. At a point 6 feet from the driveway, the height of the ramp is 18 inches. What is the rate of change of the ramp’s incline?

Between the two points, the ramp rises from 12 inches to 18 inches, a change of 6 inches. The horizontal distance changes from 4 feet to 6 feet, a change of 2 feet. The rate of change is 6 ÷ 2 = 3 inches up per foot across, so the correct choice is “3 inches up per foot across.”

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