Final answer:
The formula connecting circumference and radius is C = 2πr. The letter C represents the circumference, π is approximately equal to 3.14159, and r is the radius.
Step-by-step explanation:
The formula that relates circumference and radius is C = 2πr, where C stands for circumference, π (pi) is a constant approximately equal to 3.14159, and r represents the radius of the circle. The formula is derived from the understanding that the circumference is the total distance around the circle, and pi (π) is the ratio of the circumference to the diameter of any circle. Therefore, since the diameter is twice the radius (d = 2r), the formula for circumference using the radius is C = πd which simplifies to C = 2πr.