GCSE-ready- Home
- Lessons
- GCSE & IGCSE Mathematics
- Place value, ordering and negative numbers
Place value, ordering and negative numbers
Every digit has a value that depends on where it sits. Negative numbers follow simple rules once you picture a number line.
Place value
In 4 307.25 the 3 is worth 300, the 7 is worth 7 and the 5 is worth 5 hundredths.
To order decimals, line up the decimal points and compare digit by digit from the left.
0.45 > 0.405: both have 4 tenths, then 5 hundredths beats 0 hundredths.
To order decimals, line up the decimal points and compare digit by digit from the left.
0.45 > 0.405: both have 4 tenths, then 5 hundredths beats 0 hundredths.
Negative numbers
On a number line, numbers get smaller as you go left. −7 < −2.
Adding a negative is the same as subtracting: 5 + (−3) = 2.
Subtracting a negative is the same as adding: 5 − (−3) = 8.
Adding a negative is the same as subtracting: 5 + (−3) = 2.
Subtracting a negative is the same as adding: 5 − (−3) = 8.
Multiplying and dividing
Same signs give a positive answer. Different signs give a negative answer.
(−4) × (−3) = 12
(−20) ÷ 5 = −4
(−4) × (−3) = 12
(−20) ÷ 5 = −4
The temperature is −3 °C at night and rises by 8 degrees. Then it falls by 11 degrees. What is the final temperature?
- −3 + 8 = 5
- 5 − 11 = −6
Answer: −6 °C
Line up decimal points to compare. Adding a negative means subtract; subtracting a negative means add. Same signs multiply or divide to a positive, different signs to a negative.
The interactive lesson includes the diagrams for this topic.
Check you have got it
Answer 7 quick questions with instant marking. If you get one wrong, GCSE-ready shows you why and gives you another go. It is free, and you do not need an account.