Find the circumference of each circle given its radius or diameter

The formula for circumference is $d\pi$.

a) $d = 18$, so your circumference would be $18\pi$ inches. Since it is asking to round your answer, we need to multiply $18$ by $\pi$, which rounds to $56.55$ inches. 

b) If $r = 7$, $d = 14$. Your circumference would be $14\pi$ which equals $43.98$ m.

c) If $10$ is the diameter, your circumference would be $10\pi = 31.42$ cm. If $10$ is the radius, your circumference would be $20\pi = 62.83$ cm.

d) If $4.5$ is your diameter, your circumference would be $4.5\pi = 14.14$ feet. If $4.5$ is your radius, your circumference would be $9\pi = 28.27$ feet.

- Daisy