Cubes and Cube Roots
Arithmetic
Cubes and cube roots
( all measurements will be assumed to be in centimetres )
The volume of the cube shown is
5  5  5 which
is 125 cm3.
5cm
What is the volume
of this cube ?
3cm
Cubes and cube roots
What are the volumes of the two cubes below ?
4cm
8cm
Cubes and cube roots
Suppose now that you were told the volume of a
cube and you were asked to find the length of
the side of the cube.
For example , the cube shown has a volume of
216cm3 , what is the length of the side of the
cube?

Cubes and cube roots
Find the length of the sides of these cubes
Volume
=1000
Volume =
343
Cubes and cube roots
You are going now to use a trial and error
method to find the length of the side of the
cube. In the diagrams below you will initially
guess at the answer and then try to improve
on your guess and get a better and better
answer for the length of the side of the cube.
Try to find the length of the sides of these cubes
Try to get your
answers correct to
3 decimal places.
Volume
=75cm3
Volume =
200cm3
Cubes and cube roots
The cube root button
Look at your calculator and see if you can find
the cube root symbol.
It should look like this 3 .
You will need to press the MATHS button first
to see it if you are using a graphic calculator.
This 3 is called the cube root button.
Use it to find
325
345
3105
380
3120
3500
Cubes and cube roots
Your answers should look like those in the
diagram shown.
Look back at the answers you got for the sides of
the cubes on the previous slide. Do you see how
you might use the cube root button to help you
find the side of a cube very easily.
Cubes and cube roots
Use the cube root button on your calculator to
find the lengths of the sides of the cubes
shown.
Volume =
400cm3
Volume =
640cm3
Volume =
850cm3
Volume =
200cm3