Integer Multiplication and Division (Negatives) KS3 Revision
What you need to know
Things to remember:
- If you multiply or divide by a negative number, it changes the sign of the number it is multiplying.
- A positive becomes negative.
- A negative becomes positive.
What is the value of -7\times8?
Before we start, what is multiplication? Well, it is just a way of writing lots of additions.
So, how does this help us multiply by a negative number? It doesn’t quite yet. We also need to remember that the order of multiplication doesn’t matter.
So now, we can change the order of our multiplication and treat it like lots of additions, or, in this case, subtractions.
But, remember that 8\times7=56. So, really, all that happens when we multiply a positive number by a negative number is that it becomes negative. The sign has changed!
The same thing happens when we multiply a negative by a negative, it changes the sign, but this time to a positive.
The same thing works when dividing by a negative number too.
Positives become negative.
Negatives become positive.
Question 1: What is the value of 7\times-3?
Question 2: What is the value of -45\div-9?