Marquetta sells hand-knit sweaters at a handicrafts market. each sweater sells for
$50. the wool costs marquetta $30 per sweater and there is a booth fee of $25. how
many sweaters must she sell to make a profit?

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?