How to show the circumference of a circle is π x diameter

Part ofShape, space and measures

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A one-minute video on how to show the circumference of a circle is π x diameter. π is 3.14 to 2 decimal places.

Circumference of circle slideshow

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WHAT YOU NEED: 3 glasses, ribbon, scissors.
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STEP 1 - WRAP RIBBON: Take the ribbon and wrap it around a glass. Mark where the ribbon overlaps itself.
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STEP 2 - CUT CIRCUMFERENCE: Cut the ribbon at the point where it overlaps. You now have a piece of ribbon which is the same length as the circumference of the glass.
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STEP 3 - LINE UP 3: Line up the other 2 glasses alongside the first so you have a row of 3 circles. The total length across is now 3 diameters.
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STEP 4 - π × DIAMETER: Place the ribbon across the top of the 3 glasses…
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…and you can see that the ribbon is just over 3 times the diameter of 1 circle. This number, called π (or pi), is approximately 3.14. You have shown that the circumference of a circle is π × diameter.
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TIP: Try it with any circular object. Whatever the size, the circumference is always just over 3 × diameter.

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