Missing Numbers and Number Lines
Grade 1 · Math · Study Guide
Learn how to use a number line to find missing numbers and solve problems.
A number line is a straight line with numbers placed in order from least to greatest. The numbers are equally spaced — each step to the right is one more, and each step to the left is one less. Number lines help us add, subtract, and find missing numbers.
Sometimes a number line has a blank where a number should be. To find the missing number, look at the numbers before and after it. Count forward or backward from a known number to find what fits in the gap. For example, if you see 4, ___, 6 on a number line, the missing number is 5 because 5 comes between 4 and 6.
You can also use a number line to count patterns. If numbers go up by 2 (like 2, 4, 6, ___), the missing number is 8. Look at the pattern and continue it!
| Number Line | Missing Number | How to Find It |
|---|---|---|
| 3, 4, ___, 6, 7 | 5 | Count up 1 from 4 |
| 10, ___, 12, 13 | 11 | Between 10 and 12 |
| 6, 8, ___, 12 | 10 | Skip count by 2 |
| 15, ___, 17 | 16 | Between 15 and 17 |
| 0, 5, ___, 15 | 10 | Skip count by 5 |
Key terms
- number line
- A straight line with numbers placed in order from smallest to largest
- missing number
- A number that has been left out of a sequence that needs to be found
- sequence
- Numbers arranged in a pattern or order
- between
- A number that comes after one number and before another
Flashcards
- Number Line
- Numbers in order on a straight line, equal spaces apart
- What comes after 17?
- 18 (one step to the right on the number line)
- What comes before 9?
- 8 (one step to the left on the number line)
- Find the missing: 5, ___, 7
- 6 (it fits between 5 and 7)
- Sequence
- Numbers arranged in a special order or pattern
- Find the missing: 10, ___, 20
- 15 (halfway between 10 and 20 when counting by 5s)
Practice questions
What is the missing number? 8, 9, ___, 11
- 7
- 12
- 10
- 8
Show answer
Answer: 10
8, 9, 10, 11 — count up by 1 each time; 10 comes after 9
On a number line, numbers get bigger as you move to the right.
Show answer
Answer: True
On a number line, moving right means going higher; moving left means going lower
What number comes between 14 and 16? ___
Show answer
Answer: 15
15 is between 14 and 16 on a number line
The number line shows: 0, 2, 4, ___, 8. What is the missing number?
- 5
- 6
- 7
- 3
Show answer
Answer: 6
0, 2, 4, 6, 8 — skip counting by 2; 6 comes after 4
Which number line shows the correct order?
- 5, 3, 4, 6
- 4, 5, 6, 7
- 9, 8, 7, 10
- 1, 3, 2, 4
Show answer
Answer: 4, 5, 6, 7
Each number increases by 1 in the correct order
Fun facts
- Number lines go on forever in both directions — you can always add one more or go one less!
- Thermometers are a type of number line we use in real life to measure temperature.
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