The roof of a house needs to be resurfaced. The roof is a triangular prism where the base (b) is 20 feet, the length (d) is 40 feet, and the height (h) is 15 feet. Each side of the roof (s1 and s2) has a length of 18 feet. What is the total area that needs to be resurfaced?

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?