Revision Notes:
1. Integers include:
| Type of numbers |
Integers include |
| Whole numbers |
✅ |
| Natural numbers |
✅ |
| Negative & positive numbers |
✅ |
| Decimal |
❌ |
| Fractions |
❌ |
2. Integer properties:
| Property |
Addition |
Subtraction |
Multiplication |
Division |
| Closure |
✅ |
✅ |
✅ |
❌ |
| Commutative |
✅ |
❌ |
✅ |
❌ |
| Associative |
✅ |
❌ |
✅ |
❌ |
- Closure property: When integers are added or subtracted or multiplied, the answer is an integer.
- Commutative property:
For addition: a + b = b + a
For multiplication: a x b = b x a
For addition: a + (b + c) = (a + b) + c
For multiplication: a x (b x c) = (a x b) x c
3. Distributive Property:
- Multiplication is distributive over addition and subtraction.
- a x (b + c) = a x b + a x c
- a x (b - c) = a x b - a x c
4. Additive identity of Integers is zero.
i.e. a + 0 = 0 + a = a
5. Multiplicative identity of Integers is 1.
i.e. a × 1 = 1 × a = a
6. An integer multiplied by zero is zero. i.e. a x 0 = 0
7. Any integer divided by 1 gives the same integer, i.e. a ÷ 1 = a
8. For an integer, a ÷ 0 is not defined.
9. Rules for addition of integers:
| Sign of integers |
Operation |
Sign of answer |
Examples |
| ➕ + ➕ |
➕ |
➕ |
5 + 4 = 9 |
| ➖ + ➖ |
➕ |
➖ |
-5 + (-4) = -9 |
| ➕ + ➖ |
➖ |
Of bigger number |
2 + (-4) = -2 |
| ➖ + ➕ |
➖ |
(-3) + 5 = 2 |
10. Rules for subtraction of integers:
| Sign of integers |
Operation |
Sign of answer |
Examples |
| ➕ - ➕ |
➖ |
Of bigger number |
8 - 5 = 3 |
| 5 - 8 = -3 |
| ➖ - ➕ |
➕ |
➖ |
(-8) - 5 = -13 |
| ➖ |
(-3) - 5 = -8 |
| ➖(big) - ➖ |
➖ |
➖ |
(-5) - (-3) = -2 |
| ➖ - ➖(big) |
➖ |
➕ |
(-2) - (-5) = 3 |
| ➕ - ➖ |
➕ |
➕ |
8 - (-3) = 11 |
| 3 - (-8) = 11 |
11. Rules for multiplication & division of integers:
| Sign of integers |
Sign of answer |
Examples |
| ➕ X ➕ or ➕ ÷ ➕ |
➕ |
3 x 2 = 6 or 6 ÷ 2 = 3 |
| ➕ X ➖ or ➕ ÷ ➖ |
➖ |
3 x (-2) = -6 or 6 ÷ (-2) = -3 |
| ➖ X ➕ or ➖ ÷ ➕ |
➖ |
(-3) x 2 = -6 or (-6) ÷ 2 = -3 |
| ➖ X ➖ or ➖ ÷ ➖ |
➕ |
(-3) x (-2) = 6 or (-6) ÷ (-2) =3 |