Negative numbers · Usually met around P5
Counting through zero
Crossing 0: go to 0 first, then the rest.
How to do it
Method
Crossing 0: go to 0 first, then the rest
−4 up 9: −4 → 0 (4) → 5 (5 more)
Another way
Count the marks
−3, −2, −1, 0, 1, 2, 3, 4, 5
In full
Counting on adds 1 each time and carries on past 0: −3, −2, −1, 0, 1, 2. Counting back takes 1 away each time, and after 0 the numbers are negative: 2, 1, 0, −1, −2. 0 counts too: never skip it. When a temperature rises, count up the thermometer (right on a number line); when it falls, count down (left). Crossing 0, take it in two steps: from −4°C up 9 degrees, first go up 4 to reach 0°C, then the other 5, to 5°C. Or count the marks on the thermometer one by one.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Counting on 2 at a time: -3, -1, 1, □
Show the answer and working
Answer: 3
2 more each time: 2 more than 1 is 3. Keep going past 0.
Example 2
Counting back 3 at a time: 6, 3, 0. What comes next?
- A. -3
- B. 3
- C. 0
- D. -6
Choose the right answer
Show the answer and working
Answer: A. -3
3 less each time: 3 less than 0 is -3. Past 0, the numbers are negative.
Example 3
Counting on from -9 to 1, how many numbers do you say (counting -9 and 1)?
Show the answer and working
Answer: 11
9 negatives, then 0, then 1 positives: 9 + 1 + 1 = 11. Don't leave out 0.
Practise it in the game →Negative numbers · Free to start, unlimited questions, no download