Back to: Mathematics Primary 4
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Square of Numbers
The square of a number is the number multiplied by itself.
How to Square A Number
To square a number: multiply it by itself.
3 squared =32 = 3×3 = 9
Squared” is often written as a little 2 like this:
This says “4 Squared equals 16”
(the little 2 says the number appears twice in multiplying)
Squares From 02 to 62
| 0 Squared | = | 02 | = | 0 × 0 | = | 0 |
| 1 Squared | = | 12 | = | 1 × 1 | = | 1 |
| 2 Squared | = | 22 | = | 2 × 2 | = | 4 |
| 3 Squared | = | 32 | = | 3 × 3 | = | 9 |
| 4 Squared | = | 42 | = | 4 × 4 | = | 16 |
| 5 Squared | = | 52 | = | 5 × 5 | = | 25 |
| 6 Squared | = | 62 | = | 6 × 6 | = | 36 |
Square Root
Finding the square root of a number is the inverse operation of squaring that number. Remember, the square of a number is that number times itself.
The square root of a number, n, written below is the number that gives n when multiplied by itself.
Many mathematical operations have an inverse, or opposite, operation. Subtraction is the opposite of addition, division is the inverse of multiplication, and so on. Squaring, which we learned about in a previous lesson, has an inverse too, called “finding the square root.” Remember, the square of a number is that number times itself. The perfect squares are the squares of the whole numbers: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100 …
The square root of a number, n, written
is the number that gives n when multiplied by itself. For example,
because 10 x 10 = 100
Examples
Here are the square roots of all the perfect squares from 1 to 100.
The Square Root Symbol
 |
This is the special symbol that means “square root”, it is sort of like a tick, and actually started hundreds of years ago as a dot with a flick upwards. It is called the radical, and always makes mathematics look important! |
We use it like this:
and we say “square root of 9 equals 3”
Example: What is √25?
25 = 5 × 5, in other words when we multiply 5 by itself (5 × 5) we get 25
So the answer is:
√25 = 5
But wait a minute! Can’t the square root also be −5? Because (−5) × (−5) = 25 too.
- Well the square root of 25 could be −5 or +5.
- But when we use the radical symbol √ we only give the positive (or zero) result.
Example: What is √36 ?
Answer: 6 × 6 = 36, so √36 = 6
Try to remember them up to 12.
Perfect Squares
The Perfect Squares (also called “Square Numbers”) are the squares of the whole numbers:
|
Perfect |
|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 16 |
| 5 | 25 |
| 6 | 36 |
| 7 | 49 |
| 8 | 64 |
| 9 | 81 |
| 10 | 100 |
| 11 | 121 |
| 12 | 144 |
| 13 | 169 |
| 14 | 196 |
| 15 | 225 |
| etc… |
Quiz
- What is the square root of 8?
- What is the square root of 9?
- What is the square root of 10?
- What is 1 squared?
- What is 1.1 squared?
What is 2.6 squared?
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