A stream begins at an elevation of 2000 meters and ends in a lake at an elevation of 400 meters. The lake is 320 kilometers from the stream source. What is the average gradient of the stream?

Answer is in the file below

cutt.ly/zxt1ipy

Okay. the formula for the area of a circle is pi * r^2. the radius is half of the diameter, so the radius is 7, because that is half of 14. 7^2 is 49 and we could solve the the more precise measurement, but that’s not one of the answer choice, so the area is 49pi. the answer is d: 49.