Answer:
2
Step-by-step explanation:
[tex]C_{old}=2 \pi r = 2 \times \pi \times 3 = 6 \pi.[/tex]
Now double the radius so that [tex]r=6[/tex] then
[tex]C_{new}=2\pi r= 2 \times \pi \times 6 = 12\pi[/tex].
So the circumference is multiplied by
[tex]\frac{C_{new}}{C_{old}}=\frac{12\pi}{6\pi}=2[/tex]
when the radius is doubled.
