1. The circumference of a circle is 2πr, and when we plug in 3 for r, we get 6π.
2. We'll use the same formula and plug in 10 for r, giving us 20π.
3. The formula we use in this case is πd, and when we plug in 13 for d, we get 13π.
4. Same formula from 3, we plug in 9.5 for d and get 9.5π.
5. You can calculate the circumference of a circle using 2 formulas, C=2πr (where r=radius and C=circumference) and C=πd (where d=diameter and C is circumference).
6. You use 2πr when the radius is given.
7. You use πd when the diameter is given.
8. 2 examples could be to use the 2 formulas.
