Multiplication of Integers Rules:-
Rule 1 – In order to find the product of two integers with same signs, we simply multiply the integers regardless of their signs and give a ( + ) positive sign to the product.
Rule 2 – In order to find the product of two integers with different signs, we simply multiply the integers regardless of their signs and give a ( – ) negative sign to the product.
Multiplication of Integers Examples
Example 1
Multiply ( 10 ) by ( 7 ).
Explanation
In order to multiply two positive integers, we simply multiply the two integers, and add a positive sign to it.
Since, both 10 and 7 are positive
We simply multiply the integers:
10 x 7 = 70
and add the positive sign to the product + 70
Hence, 10 x 7 = +70 or 70
Example 2
Multiply ( -5 ) by ( -9 ).
Explanation
Multiplication of two negative integers is always a positive integer. In order to multiply two negative integers we simply multiply two numbers, and add a positive sign to it.
Since, both -5 and -9 are negative.
We simply multiply the two integers, ignoring their signs:
5 x 9 = 45
and add the positive sign to the product + 45
Hence, -5 x -9 = +45 or 45
Example 3
Multiply ( 4 ) by ( -7 ).
Explanation
Multiplication of one positive and one negative integer will always results in negative integer. In order to multiply a positive integer and a negative integer, we simply multiply the two numbers, and add a negative sign to it.
Since, 4 is positive and -7 is negative.
We simply multiply the two integers, ignoring their signs:
4 x 7 = 28
and add a negative sign to the result – 28
Hence, 4 x -7 = -28
Example 4
Multiply ( -7 ) by ( 8 ).
Explanation
Multiplication of one positive and one negative integer will always results in negative integer. In order to multiply a positive integer and a negative integer, we simply multiply the two numbers, and add a negative sign to it.
Since, -7 is negative and 8 is positive.
We simply multiply the two integers, ignoring their signs:
7 x 8 = 56
and add a negative sign to the result – 56
Hence, -7 x 8 = -56