The Circumference of a circle is how far around the outside of the circle measures. We really can't measure this with a ruler. We can place a piece of string around the outside of the circle and then lay the string in a straight line and measure that.
Another way to find the circumfernce is to measure how far it is across the middle of the circle, which is called the diameter. If we multiply that by Π (PI) which is about 3.14 we will then get the circumference.
Circumference of a Circle = 3.14 * diameter (C = Π x d)
Experiment. Trace the bottom of something that is circular on a piece of paper. Get a piece of string and wrap it around the circle. Mark on the string where the circle ends. Then measure the string up to that point with a ruler.
Now measure acoss the middle of the circle. Multiply that times 3.14. Are the two measurements the same?
The rim of the bicycle wheel shown below has a radius of 13 inches. What is the circumference of the rim of the wheel?
If the wheel revolves 3 times how many feet will it have travelled?
If the wheel revolves 400 times how many feet will the bike have travelled?
