C = πd is the formula to find the circumference of a circle, c being circumference and d being diameter.
What this formula means, is that the circumference of a circle is equal to the diameter times π, which we can approximate using 3.14.
So we multiply the diameter, 28, by 3.14 to get the circumference.
28 x 3.14 = 87.92.
The circumference of the circle is 87.92.
Hope this helps!!
