Owen loves to compete in triathlons. At a race a few months ago, he finished in 270 minutes. Yesterday, he completed another triathlon and finished in 351 minutes. What was the percent of increase in Owen's finishing time?

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?