Write the addition or subtraction rule for an input/output table – up to 20

key notes :

🔹 What is an Input/Output Table?

• It shows how numbers change from input to output.
• The input is the starting number.
• The output is the result after applying a rule.

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🔹 What is a Rule?

A rule tells what we do to the input number.

It can be:

• ➕ Addition (add a number)
• ➖ Subtraction (take away a number)

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🔹 How to Find the Rule

Look at the input and output numbers.

Ask:

• Did the number increase? ➝ Addition
• Did the number decrease? ➝ Subtraction

Find the difference between input and output.

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🔹 Steps to Write the Rule

Compare input and output.

Find how much the number changed.

Write the rule:

• Add ___
• Subtract ___

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🔹 Examples

Example 1:

• Input: 3 → Output: 7
• 3 + 4 = 7
  ✅ Rule: Add 4

Example 2:

• Input: 10 → Output: 6
• 10 − 4 = 6
  ✅ Rule: Subtract 4

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🔹 Important Points

• Numbers will be up to 20 only.
• The same rule is used for all rows.
• Check your rule with another pair to be sure.

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🔹 Quick Practice Idea 🎯

• Input: 5 → Output: 9
• Input: 6 → Output: 10
  👉 What is the rule?
  ✅ Add 4

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🌟 Teaching Tip

• Use objects like beads or fingers to help children see the change.
• Encourage students to say:
  👉 “I add ___” or “I take away ___”

Learn with an example

Let’s practice!🖊️