1.4 Negative numbers
So far you have only looked at positive numbers, but negative numbers are just as important. Negative numbers have a minus sign (–) in front of them.
Some examples of where negative numbers will apply to real life is with temperatures and bank balances, although hopefully our bank balances will not display too many negatives!
You might have encountered negative numbers in weather reports, such as temperatures like –2°C, which indicate temperatures below freezing. Freezing point, which is 0 degrees Celsius, is where water turns into ice. If you ever have an overdraft at the bank, you may see minus signs next to the figures. If a bank statement reads –£30, for example, this tells you how much you’re overdrawn. In other words, what you owe the bank!
Where have you seen negative numbers recently? Look at this thermometer:
It shows us that:
–10°C is a lower temperature than –5°C
10°C is a higher temperature than –10°C.
Hint: ‘Lower’ means ‘less than’.
‘Higher’ means ‘greater than’.
The less than < and greater than > symbols are used to compare temperatures, indicating if one temperature is lower or higher than another.
Example: 25°C > 10°C
This means that 25 degrees Celsius is greater than 10 degrees Celsius.
The lower the temperature, the colder it is, the higher the temperature, the warmer it is.
Activity 4: Using negative numbers in everyday life
- The following table shows the temperatures in several cities on one day.
| City | Temperature |
|---|---|
| A | –2°C |
| B | –5°C |
| C | –1°C |
| D | –8°C |
| E | –3°C |
- Which are the coldest and warmest cities?
A particular brand of ice cream includes the following note in its storing instructions:
- For best results, store in temperatures between –10°C and –6°C
If your freezer’s temperature was –11°C, would it be OK to keep this ice cream in it?
Answer
- City D is the coldest because it has the lowest temperature. City C is the warmest because it has the highest temperature.
- No, because –11°C is colder than the recommended range of between –10°C and –6°C. Keeping the ice cream in your freezer would probably damage the ice cream.
You have now seen how we use negative numbers in everyday life, for example bank balances and temperatures. Try practising using them when you are out and about. You will also use this skill within some simple questions that are coming up.