Polygon C has an area of 40 square units. Kennan drew a scaled version of Polygon C using a scale of 1/2 and labeled it Polygon D. What is the area of Polygon D?

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?