You want to buy a new cell phone. the sale price is $149$149. the sign says that this is $35$35 less than the original cost. what is the original cost of the phone?

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?