Final answer:
The approximate circumference of a circle with a radius of 20.5 cm can be calculated using the formula C = 2πr, which yields an answer of approximately 128.81 cm. The closest provided option to this calculation is 129 cm.
Step-by-step explanation:
To find the approximate circumference of a circle with a radius of 20.5 cm, one can use the formula:
C = 2πr
Where C is the circumference, π (pi) is a constant approximately equal to 3.14159, and r is the radius of the circle. Using the given radius:
C = 2 × π × 20.5 cm
C = 2 × 3.14159 × 20.5 cm
C ≈ 128.81 cm
The closest approximation from the provided options is:
a. 129 cm