A number line is like a ruler for numbers. The marks are spaced evenly, so every jump from one mark to the next is the same size. Skip counting (Skip Counting by 5s, 10s and 100s) helps you read it.
Why it works
From 300 to 400 is 100. There are 10 equal jumps, and 10 jumps of 10 make 100, so each jump is 10. Now count jumps from 300: 310, 320, 330, 340, 350, 360, 370. The dot is 7 jumps along, at 370.
Worked example: Find the jump size
A number line goes from 0 to 1,000 in 10 equal jumps. How big is each jump?
- Try counting by 100s: 100, 200, …, 1,000.
- That takes 10 jumps, so each jump is 100.
Answer: 100
Worked example: Count jumps, not marks
Each jump is 10. A dot is 4 jumps after 50. Where is it?
- Start at 50. Don’t count the 50 mark itself.
- Jump: 60, 70, 80, 90.
Answer: 90
Key idea
On a number line every jump is the same size. Find the jump size first, then count jumps, not marks.
Common mistake
Counting the tick marks instead of the jumps. If you count the starting mark as “1,” you end up one jump too far. Check: put your finger on the start, then count each hop to the next mark.
Grown-up tip: Draw a number line on a long strip of paper and let your child hop a toy along it.