Jenna loves to knit mittens for her friends. If she knits 3 pairs of mittens per week, how many does she make in a 4-week month?

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?