Transcript

In this video, you'll look at how to calculate the volume of prisms. A prism is a 3D shape where the cross section, or slice, of the shape is the same all the way through. You can see that a slice of any of these shapes would remain the same wherever you cut it. To calculate the volume of any prism, all you need to do is find the area of the cross section and then multiply this area by the length of the prism.

In this example, you firstly need to calculate the area of the rectangular cross section. 12 times 10 gives an area of 120 centimetres squared. Now you know the area of the cross section, all you need to do is multiply it by the length of the shape: 5 centimetres. Volume equals 120 times 5, which equals 600 centimetres cubed.

Let's try again with a different shape. Here, the cross section is the triangle. You'll recall from your earlier work that to find the area of a triangle, you use this formula. So the area of this cross section is 6 times 5, divided by 2. That is 30 divided by 2. This gives an area of 15 centimetres squared. Now, multiply the area of the cross section by the length of the shape to find the volume. 15 times 12 gives a volume of 180 centimetres cubed. Look at a couple more examples of calculating the volume of prisms, before having a go yourself.