Final answer:
The circumference of a circle varies directly with its diameter. In this case, the circumference is 44 cm when the diameter is 21 cm. The equation that relates the circumference to the diameter is c = 2.0952d.
Step-by-step explanation:
The circumference of a circle is the distance around the edge of the circle. It varies directly with the diameter, which is the distance across the circle through its center. In this case, the circumference is 44 cm when the diameter is 21 cm.
To find the constant of variation, we can set up a proportion using the given values:
c/d = k
Where c represents the circumference, d represents the diameter, and k is the constant of variation.
Plugging in the given values, we have:
44/21 = k
Solving for k gives us a constant of variation of approximately 2.0952.
Therefore, the equation that relates the circumference (c) to the diameter (d) is:
c = 2.0952d