Hey there!
C=πd
Where
C=Circumference
π=pi (3.14...)
d=diameter
So all we have to do is plug in the value of d and multiply π times 6:
C=π×6
C≈18.84 in
≈ means approximately equal to.
Hope everything is clear.
Let me know if you have any queries; if you do, kindly comment below my answer. :)
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