What is the constant of proportionality for the relationship between the length of the arc intercepted by a 80° angle and the radius of the circle

The distance around the lake is 2 kilometers. ifelena wants to run 14 kilometers this week, howmany laps must she run around the lake

Me because some of question i don’t understand

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?