Luis bought stock at $84.50. The next day, the price increased $15.10. This new price changed by -2 3/4% the following day. What was the final stock price, rounded to the nearest cent? Is your answer reasonable? Complete the explanation.

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?