Question

Rewrite the formula for the circumference of a circle C=2xpix r in terms of its diameter d. Show your work.

Answer 1

Hi there!

The answer is
$circumference \: = d\pi$
In this formula d represents the diameter.

We know that 2 times the radius equals the diameter, hence
$2r = d$

Therefore we can replace the 2r in the original formula by d, and then we get the following:
$circumference = 2\pi \: r = 2r\pi = d\pi$

Answer 2

Diameter = 2·radius

С = 2·π·r   ⇒    С = π·d