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Negative numbers
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Temperatures below zero, bank overdrafts and depths below sea level all use negative numbers. Here is how to calculate with them.
The number line
Numbers to the left are smaller. −8 < −3 < 0 < 2.
The difference between −5 and 3 is 8: count 5 steps up to 0, then 3 more.
The difference between −5 and 3 is 8: count 5 steps up to 0, then 3 more.
Adding and subtracting
Adding a negative is the same as subtracting: 6 + (−4) = 2.
Subtracting a negative is the same as adding: 6 − (−4) = 10.
−3 + 8: start at −3 and move 8 right to 5.
Subtracting a negative is the same as adding: 6 − (−4) = 10.
−3 + 8: start at −3 and move 8 right to 5.
Multiplying and dividing
Same signs give a positive answer. Different signs give a negative answer.
−4 × −5 = 20
−24 ÷ 6 = −4
7 × −3 = −21
−4 × −5 = 20
−24 ÷ 6 = −4
7 × −3 = −21
At midnight it was −6 °C. By noon it was 9 °C. By how much did the temperature rise?
- From −6 up to 0 is 6 degrees.
- From 0 up to 9 is 9 degrees.
- 6 + 9 = 15
Answer: 15 °C
Subtracting a negative means add. For × and ÷, same signs give positive and different signs give negative.
The interactive lesson includes the diagrams for this topic.
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