Please help I don’t understand this

For a circle, the circunference is equal to:

C = 2*pi*r

pi = 3.14

where r is the radius of the circle, defined as the distance between the center of the circle and the edge.

Then, in the first circle at the left, we can see that the distance between the center and the edge is the line RT or TZ, and we know that RT 2.2cm

Then the circunference of this circle is:

C = 2*3.14*2.2cm = 13.816 cm

Now for the second circle we have that the radius can be ZB or BV

We know that ZB = 5.1 in

C = 2*3.14*5.1 in = 32-028 in

maybe i can