Multiplication of integers

Multiplication of integers

When a positive number is multiplied by another positive number, the product is also a positive number.

Example 1

(a) $(+3) \times (+4) =$

Solution

There are four (4) groups of $(+3)$ each as shown in the following number line:

Therefore, $(+3) \times (+4) = +12$

(b) $+5 \times (+2)$

Solution

There are two (2) groups of $+5$ each as shown in the following number line:

Therefore, $+5 \times (+2) = 10$

When a negative number is multiplied by another negative number, the product is a positive number.

Example 3

(a) $(–2) \times (–4) = +8$

(b) $(–18) \times (–12) = +216$

(c) $(–70) \times (–55) = +3850$

When a positive number is multiplied by a negative number or a negative number is multiplied by a positive number, the product is a negative number.

Example 4

$(–3) \times (+3) =$

Solution

There are three groups of $–3$ each as shown in the following number line:

Therefore, $(–3) \times (+3) = –9$