 Introduction to bookkeeping and accounting

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

# 1.7 Negative numbers and the use of brackets

Numbers smaller than zero (shown to the left of zero on the number line in the figure below) are called negative numbers. We indicate they are negative by putting them in brackets as shown in the figure below. Figure 4

Rules of negative numbers

The rules for using negative numbers can be summarised as follows:

Addition and subtraction

• Adding a negative number is the same as subtracting a positive 50 + (-30) = 50 – 30 = 20
• Subtracting a negative number is the same as adding a positive 50 – (-30) = 50 + 30 = 80

Multiplication and division

• A positive number multiplied by a negative gives a negative 20 x -4 = -80
• A positive number divided by a negative gives a negative 20 / -4 = -5
• A negative number multiplied by a negative gives a positive -20 x -4 = 80
• A negative number divided by a negative gives a positive -20 / -4 = 5

Try to confirm the above rules for yourself by carrying out the following exercise either manually or by means of a calculator.

## Activity 9

Calculate each of the following. (In this activity we will assume the convention that if a number is in brackets it means it is negative).

(a) (2) x (3)

(a) 6

(b) 6 – (8)

(b) 14

(c) 6 + (8)

(c) (2)

(d) 2 x (3)

(d) (6)

(e) (8) / 4

(e) (2)

(f) (8) / (4)

(f) 2

## Important note

Always remember that while a single number in brackets means that it is negative, the rule of BODMAS means that brackets around an ‘operation’ between two numbers, positive or negative, means that this is the first operation that should be done. The answer for a series of operations in an example such as 12 + (-8 – 2).would thus be 2 according to the rules of BODMAS and negative numbers. Note: if 12 + (-8 – 2) was given as 12 + ((8) – 2) the answer would still be 2 as (8) is just another way of showing -8.

B190_1

### Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus