Ordering negative numbers
- On a number line, numbers get smaller as you go left. −8 is less than −3.
- The further a negative number is from zero, the smaller it is.
Adding and subtracting
- Adding a negative number is the same as subtracting: 5 + (−3) = 5 − 3 = 2.
- Subtracting a negative number is the same as adding: 5 − (−3) = 5 + 3 = 8.
- Use a number line for problems like −4 − 6: start at −4 and move 6 left to −10.
Multiplying and dividing
- If the signs are the same, the answer is positive: −6 × −4 = 24.
- If the signs are different, the answer is negative: −20 ÷ 5 = −4.
- With several numbers, count the negative signs: an even number of them gives a positive answer.
Powers of negative numbers
- (−3)² = −3 × −3 = 9, but −3² means −(3²) = −9, because the power comes before the minus sign.
- (−2)³ = −8: an odd power of a negative number is negative.
Temperatures
- The difference between 4 °C and −9 °C is 4 − (−9) = 13 degrees.
- A rise of 8 degrees from −5 °C gives 3 °C.
Key terms
- Negative number
- A number less than zero.
- Integer
- A whole number, which can be positive, negative or zero.
- Number line
- A line with numbers placed at equal intervals, used to compare and calculate.
- Difference
- The result of subtracting one number from another.
- Sign
- Whether a number is positive (+) or negative (−).