Inner diameter of the circle: 1) If the inner diameter refers to the diameter, the circumference is: 3. 14*8=25. 12 (m);

2) If the inner diameter refers to the radius, the circumference is: 3. 14*8*2=50.24 (m);

The math book says diameter and radius, and I think the inner diameter is the diameter in life. what do you think?