The circumference of a circle, C, is directly proportional to the length of its radius, r. Write down a formula,using k, connecting the circumference of the circle and the length of its radius.
The proportional relationship connecting the circumference of the circle and the length of its radius is:
[tex]C = kr[/tex]
What is a proportional relationship?
A proportional relationship is a function in which the output variable is given by the input variable multiplied by a constant of proportionality, that is:
[tex]y = kx[/tex]
In which k is the constant of proportionality.
In this problem:
The output is the circumference of the circle.
The input is the radius of the circle.
Hence, the formula is:
[tex]C = kr[/tex]
You can learn more about proportional relationships at https://brainly.com/question/25815502
