The school made 2,800 on the school carnival the second and fifth grade classes each made only $200 the kindergarten and fourth grade classes each made double the second grade amount the first and third grades made the same amount of money. how much did each grade level make

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?