Question

Driving down a​ mountain, Bob Dean finds that he descends 3200 feet in elevation by the time he is

3.9 miles​ (horizontally) away from the high point on the mountain road. Find the slope of his descent.​ (1 mile​ = 5280​ feet).

Answer 1

-0.155

Explanation:

You want the slope of Bob's descent when he descends 3200 feet in a horizontal distance of 3.9 miles.

Slope

To find the slope of Bob Dean's descent, we can use the formula:

slope = (change in elevation) / (change in horizontal distance)

Application

In this case, the change in elevation is 3200 feet and the change in horizontal distance is 3.9 miles.

slope = -3200 feet / (3.9 miles)

To convert the horizontal distance to feet, we multiply by 5280 (the number of feet in a mile)

slope = -3200 feet / (3.9 * 5280 feet)

slope = -3200 / 20,592

slope ≈ -0.1554

The slope of Bob Dean's descent is about -0.155.

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Additional comment

As a percent grade, this is a 15.5% grade, very steep. He will need to check his brakes before he starts down.