If the elevation of the head of a stream is at 900 feet, and the elevation of the mouth of the stream is 500 feet, and the distance between the two points is 20 miles, and the meandering stream flows 25 miles between those points, what is the gradient of the stream?

80 feet per mile

Explanation:

Given that a the elevation of the head of a stream is at 900 feet, and the elevation of the mouth of the stream is 500 feet, and the distance between the two points is 20 miles, and the meandering stream flows 25 miles between those points, what is the gradient of the stream?

The gradient will be calculated by using the formula

M = change in feet ÷ change in miles

Where

M = gradient of the stream.

Change in feet = 900 - 500 = 400 feet

Change in miles = 25 - 20 = 5 miles

M = 400 / 5

M = 80

Therefore, the gradient of the stream is 80 ft per mile

conservation of mass

mass before something happens = mass afterwards