the radius is the length of the line going from one side to the middle some of the questions are already like that so just copy it down some go from one side to the other so basically you have to double them ones the diameter are the length of the lines going form one side to the other and to work out the radius from a diameter u just half the diameter the circumference formula is c=2 π r which means the circumference equals 2 x π x the radius
i hoped this helped its probably a bit confusing if so just comment and i’ll help