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Tamil Nadu (TNBSE)Class 3 Mathematics★ 3-4 marks in TN Class 3 Term 1/Term 2 exams — number sequences, pattern rules, and growing/shrinking patterns

Patterns

Samacheer Kalvi (TN State Board) Class 3 Mathematics — Chapter 3, Patterns. Number patterns and odd/even sequences. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

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By the end of this chapter you'll be able to…

1Identify the rule in a number sequence: +2, −3, +5, ×2, etc.
2Extend a sequence given the rule or the first few terms
3Find missing terms in a sequence (e.g., 5, __, 15, 20, __)
4Explore odd and even number patterns: odd+odd=even, even+even=even, odd+even=odd
5Identify patterns in multiplication tables (table of 5 always ends in 0 or 5; table of 9 digits sum to 9)
6Create and extend growing geometric patterns (e.g., number of matchsticks needed for triangle patterns)

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Why this chapter matters

Class 3 patterns move beyond simple ABAB sequences to number patterns with rules. Children learn to find the rule of a sequence (add 3 each time, subtract 5, multiply by 2), extend it, and find missing terms. They explore odd and even number patterns, multiplication table patterns, and growing geometric patterns. This is pre-algebra — finding the 'nth term' without the formal notation. The child who says 'the pattern goes up by 4 each time, so the next number is 23' is doing algebraic reasoning.

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Patterns — Class 3 Mathematics (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 3 Mathematics, Chapter 3. Number patterns and odd/even sequences.

1. About this chapter

This chapter covers Patterns as part of the Class 3 Samacheer Kalvi Mathematics curriculum. It deals with number patterns and odd/even sequences and builds conceptual understanding essential for the TN School Term Exam.

By the end of this chapter, students will be able to:

Continue number sequences
Identify odd and even patterns

2. Key concepts

Concept 1: Continue number sequences.
Concept 2: Identify odd and even patterns.

3. Important terms and formulas

Term / Formula	Description
Continue number sequences…	Continue number sequences
Identify odd and even…	Identify odd and even patterns

4. Worked examples

Example 1. Applying a key concept from this chapter.

Solution: Identify the relevant principle → apply the formula or rule → state the answer with correct units.

Example 2. A typical exam-style question on patterns.

Solution: Break the problem into steps, use the appropriate formula and verify the answer.

5. Common mistakes

Mistake: Skipping units or forgetting to state them. Fix: Always write units alongside every quantity and answer.
Mistake: Confusing similar terms or concepts in this chapter. Fix: Make a comparison table of the terms during revision.

6. Practice (exam-style)

Define the main term or principle covered in Chapter 3.
Give two real-life examples related to patterns.
Solve a short numerical or descriptive question from this chapter.
State one important formula and explain each symbol.

7. Answer key (hints)

Refer to section 2 (Key concepts) above for the definition.
Examples should be drawn from daily experience and local context.
Apply the formula from section 3, show all steps clearly.
Formula with units — refer to the textbook glossary for symbol meanings.

8. Quick revision

Class 3 Mathematics — Chapter 3: Patterns.
Core idea: Number patterns and odd/even sequences.
Key outcomes: Continue number sequences; Identify odd and even patterns.
Always revise diagrams / tables from the Samacheer Kalvi textbook before the exam.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Finding the pattern rule

Look at consecutive terms: 3, 7, 11, 15, … → difference is +4 each time, so rule = 'add 4'. Next term = 19. For: 100, 90, 80, 70, … → difference is −10, rule = 'subtract 10'. Next term = 60. For: 2, 4, 8, 16, … → each term is doubled (×2). Next term = 32.

Always check the rule against at least 2-3 consecutive differences to make sure it is consistent. A pattern must repeat the rule at every step.

Odd and Even patterns

Odd numbers: 1, 3, 5, 7, 9, … (not divisible by 2). Even numbers: 2, 4, 6, 8, 10, … (divisible by 2). odd + odd = even (3+5=8). even + even = even (4+6=10). odd + even = odd (3+4=7). odd × odd = odd (3×5=15). even × any = even (4×3=12).

These rules work for any odd/even numbers. A number ending in 1, 3, 5, 7, or 9 is odd. A number ending in 0, 2, 4, 6, or 8 is even.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Assuming the pattern is always addition/subtraction — missing multiplication patterns

✓ Check: 3, 6, 12, 24, … — differences are +3, +6, +12 (not constant). Try multiplication: each term is 2× the previous. This is a geometric sequence, not arithmetic.

WATCH OUT

✗ Applying the wrong rule because only the first difference was checked

✓ In 2, 4, 7, 11, … differences are +2, +3, +4 — the pattern is NOT constant addition, it is an increasing addition. Always check at least 2-3 steps before declaring the rule.

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