By definition, multiplication is the repeated addition of numbers. But the rules for multiplication of integers are different from that of addition. It includes three possibilities. They are:
- Multiplication between two positive numbers,
- Multiplication between two negative numbers; and
- Multiplication between a positive number and a negative number.
The product of two integers with similar sign numbers will always be positive. This means the product of two positive numbers or two negative numbers will always be positive. While the product of a positive number and a negative number (integers with different signs) will always be negative.
Rules of Multiplication
| Type of Numbers | Operation | Result | Example |
| Positive x Positive | Multiply | Positive (+) | 1 x 5 = 5 |
| Negative x Negative | Multiply | Positive (+) | (-1) x (-5) = 5 |
| Positive x Negative | Multiply | Negative (-) | 1 x (-5) = -5 |
| Negative x Positive | Multiply | Negative (-) | (-1) x 5 = -5 |
In case of multiplication of integers, just multiply the numbers without the sign. Once the product is obtained give the sign according to the rule of multiplication given in the above table.
Since multiplication is commutative property i.e. -4×3 = 3×-4 the result will be same .Hence, the 3rd and 4th rules in the table are equivalent.
Note:
- If number of negative integers to multiply is odd, the product will be negative
(Ex:−2×−4×−3 = −24).
- If number of negative integers to multiply is even, the product will be positive
(Ex:−4×−3 = 12))
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