Respuesta :

The circumference of a circle is proportional to its diameter.

[tex]C\propto d\\ \\ \therefore \quad C=kd[/tex]

Now, when d=1, C=π, therefore:

k=π

This means that:

[tex]C=\pi d[/tex]

If C=15π:

15π=πd

Therefore:

d=15