**Cube Roots** *KS3 Revision*

## What you need to know

**Things to remember:**

- It is easier to learn some of the basic cube roots instead of trying to find them each time.

Although we’re going to be looking at cube rooting, it is best to start refreshing on an easier topic, squaring and square rooting.

Squaring just means multiplying a number by itself:

5^2=5\times5=25

9^2=9\times9=81

11^2=11\times11=121

Square rooting tells us what number we multiply by itself to make our original number.

\sqrt{25}=5

\sqrt{81}=9

\sqrt{121}=11

We have seen cubing before, this is just the “mathy” word for “power of 3”

4^3=4\times4\times4=64

7^3=7\times7\times7=343

10^3=10\times10\times10=1000

So, if square rooting tells us what we multiply by itself to find our number, what do you think cube rooting might be?… Cube rooting just tells us what we multiply by itself twice to make our starting number. We write this like a square root, but with a little 3 on the left.

\sqrt[3]{64}=4

\sqrt[3]{343}=8

\sqrt[3]{1000}=10

Finding cube roots can be difficult, so it can be helpful to learn the first 10.

Number Cube Root

1 1

8 2

27 3

64 4

125 5

216 6

343 7

512 8

729 9

1000 10

## Example Questions

**Question 1:** What is the cube root of 343?

\sqrt[3]{343}=7

**Question 2:** What is the cube root of 729?

\sqrt[3]{729}=9