Aset of pencils sells for $1.75 and costs $0.40 to make. twenty percent of the profit (the difference between the purchase price and the amount it costs to make) from each set of pencils goes to a school. if 500 sets are sold, what is the amount of money that will go to the school?

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?