Squared Numbers
The examples below show how squares can be found.
| Number |
Multiplied by itself |
Square |
| 1 |
1 x 1 |
1 |
| 2 |
2 x 2 |
4 |
| 3 |
3 x 3 |
9 |
| 4 |
4 x 4 |
16 |
| 5 |
5 x 5 |
25 |
| 6 |
6 x 6 |
36 |
| 7 |
7 x 7 |
49 |
| 8 |
8 x 8 |
64 |
| 9 |
9 x 9 |
81 |
| 10 |
10 x 10 |
100 |
| 11 |
11 x 11 |
121 |
| 12 |
12 x 12 |
144 |
| 13 |
13 x 13 |
169 |
| 14 |
14 x 14 |
196 |
| 15 |
15 x 15 |
225 |
|
 |
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
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 x 9 = |
81 |
9 |
2 x 2 = |
4 |
2 |
|
10 x 10 = |
100 |
10 |
3 x 3 = |
9 |
3 |
|
11 x 11 = |
121 |
11 |
4 x 4 = |
16 |
4 |
|
12 x 12 = |
144 |
12 |
5 x 5 = |
25 |
5 |
|
13 x 13 = |
169 |
13 |
6 x 6 = |
36 |
6 |
|
14 x 14 = |
196 |
14 |
7 x 7 = |
49 |
7 |
|
15 x 15 = |
225 |
15 |
8 x 8 = |
64 |
8 |
|
16 x 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.
Writing Square Roots
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.
| What
is the square root of 42? |
| What two squares does 42 come between? |
36 and 49 |
| What are the square roots of 36 and 49 |
6 and 7 |
So the square root of 42 is between
6 and 7.
Let's use some trial and error to get an approximate answer. |
| Let's try 6.5 |
42 ÷ 6.5 = 6.46 |
We're looking to get the number we divide
by to be as close to the answer we get as possible. In this case
we have 6.5 and 6.46
Close, but we can get closer. |
| Let's take the average of 6.5 and 6.46 and try that. |
42 ÷ 6.48 = 6.48 |
| So we have an square root that is accurate
to two decimal places. You can repeat these steps to get as accurate
an answer as you want. |
Squares and Square Roots Chart
This printable version of the squares
and roots chart above will help visualize the relationship
between squares and square roots.
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