Let us find the circumference of each circle.
The circumference of a circle is given by
[tex]C=2\pi r\: \: or\: \: C=\pi D[/tex]
Where r is the radius and D is the diameter of the circle.
Circle 1:
Here we are given the diameter of the circle
D = 21 cm
[tex]C=\pi D=\frac{22}{7}\cdot21=22\cdot3=66\operatorname{cm}[/tex]
So, the circumference of the circle is 66 cm.
Circle 2:
Here we are given the diameter of the circle
D = 91 ft
[tex]C=\pi D=\frac{22}{7}\cdot91=286\: ft[/tex]
So, the circumference of the circle is 286 ft.
Circle 3:
