The table shows the balance of an account each year. Years Balance
0 $40
1 $42
2 $44
3 $46
What is the interest rate of the account? What is the balance after 10 years?

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?