Surface area of a sphere

The formula for the surface area of a sphere is:

`4pir^2`

We know that the area of a circle is:

We know how to find the radius of a circle - Pie r squared

Area = `\pir^2`

So what this is saying is that the surface area of a sphere is 4 of these.

The surface area of a sphere is just 4 flat circles they just need adding together

So the certain way for you to ensure you never ever forget the surface area of a sphere is to carry out the orange experiment.

The orange experiment

To find a surface area of a sphere take an orange

The orange experiment is as follows:

Stage 1 – Take an orange

To find a surface area of a sphere take an orange

Stage 2 – Cut the orange in half

Cut in half

Stage 3 – Using one half of the orange draw four circles around it on a piece of paper.

Draw around the slices

Draw around the slices making 4 circles

Stage 4 – Now peel the orange and place the pieces in each of the circles

Place the peelings in all of the circles, you will find that the peels exactly fit into the circles

Now you can see that, Yes! The surface area of an orange or any sphere really does cover four drawn out circles.

And therefore

Surface area of a sphere = `4timesArea\ of\ the\ ci\rc\l\e`

Surface area of a sphere = ` 4\ \pir^2`

Try it on the kitchen table now!