Buying a home for 244800 he is making a 15% down payment and financing the rest with a 25-year loan at 5.25 interest what would his monthly payment be

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?