Acar dealer sold 2 cars for $1980 each. on the first car he made a 10 percent profit while on the second car he took a loss of 10 percent. taken together, did he profit or lose on the deals?

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?