Grade 2 · Maths · Lessons
Jumps on the number line
🐸frog➡️forward⬅️back📏line
Hop along the line.The big ideaJump the tens, then the ones. Count the spaces, not the marks.
How it works
On a number line you add by jumping forward and take away by jumping back.
Jump the tens first, then the ones. Land on a ten if you can.
Count the spaces between marks, not the marks.
Example 1: Jump back to take away
- Take away 9 from 19. Start at 19.
- Jump back 9 and land on 10: 19 − 9 = 10.
- The answer is 10.
Example 2: Find the dot
- A number line counts by fives: 80, 85, 90. The dot is on the mark after 80.
- Count on one jump of five from 80: 80 + 5 = 85.
- The dot is on 85.
Example 3: The missing jump
- 31 + ? = 45. Start at 31 and aim for 45.
- Jump to 40, which is +9. Then jump to 45, which is +5.
- 9 + 5 = 14, so 31 + 14 = 45 and the missing jump is 14.
Words to know
- number line
- A line with numbers in order.
- jump
- A move along the line that adds or takes away.
Watch out
- Count spaces, not marks.
- Check what each mark counts for.
- Backward jumps take away.
Try it
- Start at 40 and jump forward 10. Where do you land?
- Start at 27 and jump back 7. Where do you land?
- A line counts by fives: 50, 55, 60. What is halfway between 50 and 60?
- Do you count the marks or the spaces?
Answers: 1. 50 · 2. 20 · 3. 55 · 4. the spaces
For grown-upsDraw a number line on the pavement with chalk and let your child hop along it.