The temperature at 7 p. m. at a weather station in minnesota was −5 °f. the temperature began changing at the rate of −2.5 °f per hour. what was the temperature at 10 p. m.?

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?