Sam travel to Miami by car going there took nine hours and the return trip lasted three hours Sam average speed of 60 mph while returning find the average speed of the trip there

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?