A toy store is ordering 3 thousand remote control cars. The store can order the cars in sets of 10 how many sets of 10 does the store need order?

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?