📘 Class 1 Mathematics – Chapter 2: Addition and Subtraction within 20
Revision Notes with Solutions and Answers
1. Addition (Adding Numbers within 20)
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Addition means joining two or more groups to find the total.
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Symbol: +
Example 1:
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7 + 5 = ?
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Count objects: 🍎🍎🍎🍎🍎🍎🍎 + 🍎🍎🍎🍎🍎 → 12
Answer: 12
Example 2:
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9 + 6 = ?
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Count: 🍌🍌🍌🍌🍌🍌🍌🍌🍌 + 🍌🍌🍌🍌🍌 + → 15
Answer: 15
Tip: Use fingers or objects to make addition easy.
2. Subtraction (Subtracting Numbers within 20)
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Subtraction means taking away some objects from a group.
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Symbol: –
Example 1:
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14 – 6 = ?
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Start with 14 apples 🍎🍎🍎🍎🍎🍎🍎🍎🍎🍎🍎🍎🍎🍎
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Take away 6 → 🍎🍎🍎🍎🍎🍎🍎🍎
Answer: 8
Example 2:
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11 – 5 = ?
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Start with 11 bananas 🍌🍌🍌🍌🍌🍌🍌🍌🍌🍌🍌
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Take away 5 → 🍌🍌🍌🍌🍌🍌
Answer: 6
Tip: Use number line for subtraction – jump backward.
3. Addition and Subtraction Word Problems
Example 1 (Addition):
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Riya has 7 pencils. She buys 4 more. How many pencils does she have now?
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Solution: 7 + 4 = 11
Answer: 11 pencils
Example 2 (Subtraction):
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There are 15 candies. Rohan eats 6 candies. How many candies are left?
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Solution: 15 – 6 = 9
Answer: 9 candies
4. Missing Number Problems
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Find the missing number in addition or subtraction:
Example 1:
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8 + ? = 14 → ? = 6
Answer: 6
Example 2:
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? – 5 = 7 → ? = 12
Answer: 12
5. Practice Questions
1️⃣ 6 + 7 = ? → 13
2️⃣ 12 – 8 = ? → 4
3️⃣ 9 + 9 = ? → 18
4️⃣ 15 – 7 = ? → 8
5️⃣ 4 + 11 = ? → 15
6️⃣ 20 – 5 = ? → 15
7️⃣ 7 + ? = 13 → 6
8️⃣ ? – 6 = 9 → 15
✅ Quick Tip for Revision:
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Use objects, toys, or fingers to visualize addition and subtraction.
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Learn adding and subtracting numbers up to 20 thoroughly.
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Solve word problems slowly, step by step.
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Practice missing number problems for better understanding.