Which is the best rational approximation for the square root of 55 ? A: 7.5
B: 5.5
C: 11.0
D: 27.5

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?