Two math teachers surveyed students on the number of hours they spend during the school week on the internet compared to the number of chores they are responsible for. The scatter plots below show the results of the survey.

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?