The intensity of a light source varies inversely as the square of the distance from the source. if the intensity of a light bulb is 400 lumen/m^2 (lux) at a distance of 3 m, determine the intensity at 10 m. round your answer to the nearest hundredth, if possible.

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?