Subtraction input/output tables – up to 18
key notes :
What is an Input/Output Table?
It is a table that shows numbers going in (input) and numbers coming out (output) after a rule is applied.
For subtraction, the rule is “subtract a number”.
Parts of the Table:
Input: The starting number.
Rule: Tells us what to do (e.g., subtract 2).
Output: The result after subtracting.
Example Table (Subtract 3):
| Input | Rule | Output |
|---|---|---|
| 10 | subtract 3 | 7 |
| 12 | subtract 3 | 9 |
| 15 | subtract 3 | 12 |
Steps to Use the Table:
Look at the input number.
Check the rule (what to subtract).
Subtract the number from input → get the output.
Practice Tip:
Start with numbers up to 18.
Check your answer by doing Output + Subtracted Number = Input. ✅
Why It’s Important:
Helps to see patterns in subtraction.
Makes solving problems faster and easier.
Strengthens mental math skills.
Fun Tip with Emojis 🎨:
Input 🟢 → Subtract ➖ → Output 🔵
Example: 🟢10 ➖ 3 = 🔵7
Learn with an example
Complete the table.
Rule: subtract 2
| In | Out |
| 2 | |
| 5 | |
| 6 | |
| 8 | 6 |
solution:
Start with the numbers in the “In” column. Subtract 2 from each number.
| 2 | − | 2 | = | 0 |
| 5 | − | 2 | = | 3 |
| 6 | − | 2 | = | 4 |
| 8 | − | 2 | = | 6 |
Write the answers in the table:
| In | Out |
| 2 | 0 |
| 5 | 3 |
| 6 | 4 |
| 8 | 6 |
Complete the table.
Rule: subtract 5
| In | Out |
| 5 | |
| 7 | |
| 8 | 3 |
| 9 |
solution:
Start with the numbers in the “In” column. Subtract 5 from each number.
| 5 | − | 5 | = | 0 |
| 7 | − | 5 | = | 2 |
| 8 | − | 5 | = | 3 |
| 9 | − | 5 | = | 4 |
Write the answers in the table:
| In | Out |
| 5 | 0 |
| 7 | 2 |
| 8 | 3 |
| 9 | 4 |
Complete the table.
Rule: subtract 1
| In | Out |
| 2 | |
| 7 | |
| 8 | 7 |
| 9 |
Start with the numbers in the “In” column. Subtract 1 from each number.
2 − 1 = 1
7 − 1 = 6
8 − 1 = 7
9 − 1 = 8
Write the answers in the table:
| In | Out |
| 2 | 1 |
| 7 | 6 |
| 8 | 7 |
| 9 | 8 |
Let’s practice!🖊️
