The high temperatures for the last seven days are: High Temperatures: 81, 78, 83, 89, 80, 87, 78 Find the RANGE of the temperatures.

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?