Answer:
56.52 km
Step-by-step explanation:
You can use this formula to find the circumference.
[tex]C =\pi \:d[/tex]
Here,
C = circumference
d = diameter
Let us solve now.
[tex]C =\pi \:d[/tex]
C = 3.14 × 18 km
C = 56.52 km
Hope this helps you.
Let me know if you have any other questions :-)