ALgebra 2 variation check description

Question

The load L, in pounds, on a certain sail varies directly as the square of the wind speed v, in miles per hour. If the load on a sail is 720 lb when the wind speed is 20 mph, what is the load on the sail when the wind speed is 10 mph?

Answer 1

From the first sentence L = kv², where k is a constant

You know L=720 when v = 20.

Using these find k.

Then knowing k, you can answer the question (find L when v=10)