Class 2 Notes - Computation Operations

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1. Introduction

This chapter introduces students to the four main arithmetic operations: Addition, Subtraction, Multiplication, and Division. Each operation helps solve everyday problems involving counting, combining, sharing, and comparing.

2. Addition (➕)

Addition means putting things together to find out how many in all.

Example: 12 + 5 = 17
Real life: I have 3 apples, my friend gives me 2 → 3 + 2 = 5
  • Start from ones place
  • Add two-digit numbers (with/without carry)
  • Used in problems like "how many in all?"

3. Subtraction (➖)

Subtraction means taking away. It tells us how many are left.

Example: 15 − 7 = 8
Real life: 10 chocolates – 3 eaten = 7 left
  • Subtract from the right
  • Use borrowing when needed
  • Used in problems like "how many left?"

4. Addition and Subtraction Together

Sometimes both operations are used together.

Example: 25 + 13 − 8 = 30

You can check subtraction by reversing the operation using addition.

5. Multiplication (✖️)

Multiplication is repeated addition. It's used to find how many in total when we have equal groups.

Example: 3 × 4 = 12 → 4 + 4 + 4 = 12
Real life: 4 baskets with 6 mangoes each = 24
  • Build tables from 2 to 10
  • Use objects and pictures to show groups
  • Learn through skip counting

6. Division (➗)

Division means sharing or grouping equally.

Example: 12 ÷ 4 = 3
Real life: 20 pencils shared among 5 friends = 4 pencils each
  • Use grouping or repeated subtraction
  • Opposite of multiplication
  • Use pictures or counters for practice

7. Word Problems

  • Addition: Rina has 24 stickers. Her brother gives 13 more. Total = ?
  • Subtraction: 30 balloons – 12 fly away = ?
  • Multiplication: 6 chocolates in 5 boxes = ?
  • Division: 20 pencils ÷ 5 students = ?

8. Estimation

Estimate by rounding off numbers to 10s or 100s. It helps solve problems quickly in your head.

Example: 48 + 23 ≈ 50 + 20 = 70

9. Using Number Line

  • For addition → jump to the right
  • For subtraction → jump to the left
  • For multiplication → equal jumps
  • For division → grouping jumps

10. Relationships

  • Addition ↔ Subtraction (opposite operations)
  • Multiplication ↔ Division (opposites)

If 7 + 5 = 12, then 12 − 5 = 7

If 4 × 3 = 12, then 12 ÷ 4 = 3

11. Mental Maths

  • Break numbers: 47 + 25 = (40 + 20) + (7 + 5) = 72
  • Use known facts: 2 × 5 = 10 → 4 × 5 = 10 + 10 = 20

12. Fun Activities

  • Use dice to roll and add
  • Flashcards for tables
  • Story sums using toys or snacks

13. Practice Questions

  • Add: 34 + 27 = ?
  • Subtract: 65 − 29 = ?
  • Multiply: 4 × 3 = ?
  • Divide: 20 ÷ 4 = ?

14. Summary Table

Operation Meaning Symbol Example Key Words
Addition Put together + 8 + 5 = 13 Total, Altogether
Subtraction Take away − 12 − 4 = 8 Left, Difference
Multiplication Repeated addition × 3 × 4 = 12 Times, Groups of
Division Share equally ÷ 20 ÷ 5 = 4 Each gets, Divided among

15. Conclusion

The chapter "Computation Operations" gives young learners the basic tools for handling numbers in everyday situations. With regular practice, play-based learning, and a focus on understanding over memorization, children build strong math foundations.