Calculate Circle Area: Converting 7cm Diameter Using π

Question

Given that the diameter of the circle is 7 cm

What is the area?

00:00 Find the area of the circle

00:03 The diameter of the circle equals twice the radius

00:07 Let's isolate radius R, this is radius R

00:13 Let's use the formula for calculating circle area

00:18 Let's substitute the radius value and solve for the area

00:33 And this is the solution to the problem

First we need the formula for the area of a circle:

$\pi r^2$

In the question, we are given the diameter of the circle, but we still need the radius.

It is known that the radius is actually half of the diameter, therefore:

$r=7:2=3.5$

We substitute the value into the formula.

$\pi3.5^2=12.25\pi$

$12.25\pi$ cm².