It takes kayla 12 minutes to walk from her house and her grandpa's house she walks to and from their house twice a week about how many minutes each week does kale has been walking between the two houses

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?