The equation 2πr is used to find circumference. To find the diameter, you will first need to find the radius, and in order to find the radius, you need to isolate "r" in the equation.
2πr = 26
Divide 2 for both sides.
πr = 13
Divide π (I am assuming π is 3.14) for both sides.
r = 4.140127389
Our radius is about 4.140127389. To find the diameter, multiply your radius by 2. This gives us 8.276057041, which rounds to 8.3 cm.
