Note on Multiplying Integers

Multiplying Integers :

In this lesson let me help you go through more on multiplying integers. Let us start with a quick review of the terms related to multiplication. The numbers to be multiplied are the factors and the result of multiplication is called as product.

4 × 5 = 20

4 and 5 are factors and 20 is the product.

There are four possibilities of multiplying two factors

Case 1: Both the factors are positive: When both the factors are positive, multiply the factors and the product is always positive. 3 × 5 = 15

Case 2: One factor is positive and the other is negative: When one of the factors is negative and the other is positive that is when the factors are of opposite signs, multiply the factors and the product has a negative sign. -3 × 5 = -15 or 3 × -5 = -15

Case 3: Both the factors are negative: When both the factors are negative, multiply the factors and then the product is always positive. -3 × -4 = 12

Case 4: One of the factors is zero: When one of the factors is zero, then the product is always zero. 0 × 6 = 0 or -5 × 0 = 0 Remember that zero is neither positive nor negative.

In short, when we multiply two Integers,

a) If the factors are of the same sign then the product is always positive.

b) If the factors are of the opposite signs then the product is always negative.

Here is an easy way to remember the sign rules for multiplication

(+) × (+) = (+)

(+) × (-) = (-)

(-) × (+) = (-)

(-) × (-) = (+)