# How far have you driven?

## “Circumference” and making the robot move forward

The “circumference” of the circle is the distance around the circle, and the “radius” is the distance from the center of the circle to the edge of the circle.

If a car wheel (which is a circle with a circumference of 100 inches) rotates 5 times, how far does the car go? How would you find that?

You would rotate the wheel once, and find that it has travelled 100 inches, because the wheel would trace out it’s circumference on the ground. Then, you would rotate it a second time, and see it move another 100 inches. Then a third, a fourth and a fifth time, and see the wheel has traced out it’s circumference on the ground 5 times.

## How far have you driven?

The amount it has travelled is 5 times the circumference. This can be used for any number of rotations. If you rotate the wheel 3 times, you would move forward 3 times the circumference (300 inches), if you rotated it 1 and a half times, you would move forward one and a half times the circumference (150 inches).

This is going to be super useful when you need to make the robot go forwards a certain distance, or when you need to calculate how far the robot has moved!