Squares and Square Roots

The square of a number?

When we multiply an integer by itself we call the product the square of the number.
For example: 4 x 4 = 16
The square of 4 is 16
The pictures above show why we call these products squares.

Squared Numbers

The examples below show how squares can be found.

Number	Multiplied by itself	Square	Number	Multiplied by itself	Square
1	1 x 1	1	9	9×9	81
2	2 x 2	4	10	10×10	100
3	3 x 3	9	11	11×11	121
4	4 x 4	16	12	12×12	144
5	5 x 5	25	13	13×13	169
6	6 x 6	36	14	14×14	196
7	7 x 7	49	15	15×15	225
8	8 x 8	64

Squared Words!

You’ll hear different words used when people talk about squares. e.g.

• Square of a number: 25 is the square of 5
• Squaring a number: multiplying the number by itself
• A squared number: 100 is a square number
• 3 squared: 3 squared is 9
• What’s the square of 9? The square of 9 is 81
• Perfect square: Perfect square is another term for square number

Make sure your children know the short way of finding a square on a calculator. e.g. to find 6 x 6, enter 6, x, =

Writing squares

Squares are powers of two.

We write squares using the same notation that we use with other powers.
e.g. for 3 squared (or 3 x 3)
we write 3²

We could talk about 3 to the power of 2, or the second power of three but we don’t usually do so; we say 3 squared. We write 3²

Square Roots

You can think of finding square roots as the opposite of finding squares. You find the square root of a number (let’s call it number A) by finding the number that, when multiplied by itself produces number A. The examples below show this:

	Number	Square Root		Number	Square Root
1 x 1 =	1	1	9×9	81	9
2 x 2 =	4	2	10×10	100	10
3 x 3 =	9	3	11×11	121	11
4 x 4 =	16	4	12×12	144	12
5 x 5 =	25	5	13×13	169	13
6 x 6 =	36	6	14×14	196	14
7 x 7 =	49	7	15×15	225	15
8 x 8 =	64	8	16×16	256	16

Note: Think of these examples: 4 x 4 = 16 and – 4 x – 4 = 16.
Positive numbers have two square roots; a positive (called the principal square root) and a negative. Unless you are asked for the negative square root, you can just give the principal square root.

When exploring squares and square roots with your children, emphasize that each process is the inverse of the other. In other words, one undoes the other.

Writing Square Roots

Make sure that your children know the square root symbol and that they can find and use it on a calculator.

Calculating and Estimating Square Roots

Most calculators have a square root button that quickly calculates square roots. There are other ways of calculating square roots but they aren’t quick. If you need an approximate value for a square root you can use a method like the one below.

Squares and Square Roots Charts

There are two square number charts, both shown above. You will find the printable version of the one on the left here and the 1² to 15² one on the right here.