Can You See the Pattern — Class 5 Mathematics (CBSE)
Based on the NCERT Math Magic Grade 5 textbook. Find patterns in numbers and shapes, then solve the practice set without looking at the answers.
1. Why this chapter matters
Patterns are the language of mathematics. They help us predict, generalise, and understand how numbers and shapes behave. This chapter develops observation skills by exploring number patterns, magic squares, calendar patterns, coding and decoding, and special sequences like hexagonal numbers. Pattern recognition is a key skill for algebra, puzzles, coding, and logical reasoning.
2. Number patterns
A number pattern is a sequence of numbers that follows a rule.
Pattern 1: Adding a constant
2, 4, 6, 8, 10... (add 2 each time — even numbers) 5, 10, 15, 20, 25... (add 5 each time — multiples of 5)
Pattern 2: Multiplying by a constant
1, 2, 4, 8, 16... (multiply by 2 each time) 1, 3, 9, 27, 81... (multiply by 3 each time)
Pattern 3: Alternating operation
1, 2, 3, 6, 7, 14, 15... (add 1, multiply by 2, add 1, multiply by 2...)
Pattern 4: Difference increases
1, 3, 6, 10, 15... (add 2, then 3, then 4, then 5 — triangular numbers)
| Position (n) | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| Triangular number | 1 | 3 | 6 | 10 | 15 | 21 |
| Difference | — | +2 | +3 | +4 | +5 | +6 |
3. Magic squares
A magic square is a grid of numbers where each row, each column, and both diagonals add up to the same total (the magic constant).
3 x 3 magic square
| 2 | 7 | 6 |
|---|---|---|
| 9 | 5 | 1 |
| 4 | 3 | 8 |
Check: Row 1: 2 + 7 + 6 = 15 Row 2: 9 + 5 + 1 = 15 Row 3: 4 + 3 + 8 = 15 Column 1: 2 + 9 + 4 = 15 Column 2: 7 + 5 + 3 = 15 Column 3: 6 + 1 + 8 = 15 Diagonal (top-left to bottom-right): 2 + 5 + 8 = 15 Diagonal (top-right to bottom-left): 6 + 5 + 4 = 15
Magic constant = 15
How to complete a magic square
If some numbers are missing, use the property that all rows, columns, and diagonals add to the same total.
Example: Complete this 3x3 magic square (magic constant = 18):
| 8 | ? | 4 |
|---|---|---|
| ? | 6 | ? |
| 3 | ? | 7 |
Solution:
- Top row: 8 + ? + 4 = 18, so ? = 6
- Left column: 8 + ? + 3 = 18, so ? = 7
- Bottom row: 3 + ? + 7 = 18, so ? = 8
- Right column: 4 + ? + 7 = 18, so ? = 7
- Middle row: 7 + 6 + ? = 18, so ? = 5
Completed square:
| 8 | 6 | 4 |
|---|---|---|
| 7 | 6 | 5 |
| 3 | 8 | 7 |
4. Calendar patterns
A calendar hides many number patterns.
Pattern 1: Dates in a row
Look at any row of 7 days in a calendar. The numbers increase by 1 each day. The total of any complete row = 7 x (middle number).
Pattern 2: 3x3 block
Pick any 3x3 block of dates. The sum of all 9 numbers = 9 x (middle number).
Example: For the block 5-11 in a month:
| 5 | 6 | 7 |
|---|---|---|
| 12 | 13 | 14 |
| 19 | 20 | 21 |
Middle number = 13. Sum = 9 x 13 = 117. Check: 5 + 6 + 7 + 12 + 14 + 19 + 20 + 21 + 13 = 117. Yes!
Pattern 3: Sum of opposite corners
In the same 3x3 block, sum of top-left + bottom-right = sum of top-right + bottom-left. 5 + 21 = 26 and 7 + 19 = 26.
5. Coding and decoding
Patterns help us create and break codes.
Simple coding rules
| Rule | Input | Output |
|---|---|---|
| Add 2 to each digit | 3, 7, 1 | 5, 9, 3 |
| Multiply by 3 then add 1 | 2, 4, 6 | 7, 13, 19 |
| Reverse the digits | 123 | 321 |
| Replace each letter with position in alphabet | A=1, B=2... | C A T = 3, 1, 20 |
Decoding: Find the rule
Sequence: 5, 8, 11, 14, 17, ? Rule: Add 3 each time. Next number = 20.
Sequence: 2, 6, 18, 54, ? Rule: Multiply by 3 each time. Next number = 162.
Sequence: 100, 90, 81, 73, ? Rule: Subtract 10, then 9, then 8... Next subtract 7. Next number = 66.
6. Hexagonal numbers
Hexagonal numbers are numbers that can be arranged as a hexagon pattern.
The sequence of hexagonal numbers: 1, 6, 15, 28, 45...
| Position (n) | Hexagonal number | Pattern |
|---|---|---|
| 1 | 1 | 1 |
| 2 | 6 | 1 + 5 |
| 3 | 15 | 6 + 9 |
| 4 | 28 | 15 + 13 |
| 5 | 45 | 28 + 17 |
The difference increases by 4 each time: +5, +9, +13, +17...
7. Activity corner
Activity 1: Create your own 3x3 magic square using numbers 1 to 9 (not in order). Verify that all rows, columns, and diagonals add up to 15.
Activity 2: Take a calendar page for any month. Pick four dates that form a 2x2 block. Find the sum. How does each sum relate to the smallest number?
Activity 3: Create a secret code where each letter gets a symbol. Write a short message in your code. Ask a friend to decode it.
Activity 4: Draw hexagonal patterns by arranging dots in hexagon shapes. Verify the first four hexagonal numbers.
8. Common mistakes
- Mistake: Assuming a pattern always uses the same operation Fix: Check the differences between consecutive terms. If they change, the rule may involve a variable difference.
- Mistake: Forgetting to check both diagonals in a magic square Fix: Always verify all rows, all columns, and both diagonals before declaring a solution.
- Mistake: Writing the next term without confirming the rule Fix: State the rule explicitly (e.g., 'add 3 each time'), then apply it to find the next term.
9. Key facts
- Number patterns follow a rule. Find the rule, predict the next term.
- Magic squares: all rows, columns, and diagonals add to the same total.
- Calendars show multiple number patterns — explore a calendar page.
- Coding replaces information using a secret rule.
- Hexagonal numbers grow by increasing differences.
- Pattern spotting is a foundation for algebra and coding.
10. Self-test
- Find the next term: 3, 6, 9, 12, ?
- Is this a magic square? Check.
| 4 | 9 | 2 |
|---|---|---|
| 3 | 5 | 7 |
| 8 | 1 | 6 |
- If a code adds 3 to each digit, what does 472 become?
- What is the 4th hexagonal number?
- A 3x3 calendar block has middle number 16. What is the sum of all 9 numbers?
11. Answer key
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Find the next term: 3, 6, 9, 12, ? Answer: 15. The rule is 'add 3 each time'. 12 + 3 = 15.
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Is this a magic square? Answer: Yes. Row 1: 4+9+2=15. Row 2: 3+5+7=15. Row 3: 8+1+6=15. Column 1: 4+3+8=15. Column 2: 9+5+1=15. Column 3: 2+7+6=15. Diagonals: 4+5+6=15 and 2+5+8=15. Magic constant = 15.
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If a code adds 3 to each digit, what does 472 become? Answer: 7, 10, 5. But 10 is two digits, so we write 705 (or 7-10-5 as separate digits).
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What is the 4th hexagonal number? Answer: 28. The sequence is 1, 6, 15, 28, 45...
-
A 3x3 calendar block has middle number 16. What is the sum of all 9 numbers? Answer: 9 x 16 = 144.
12. Quick revision
- Find the rule in number patterns by looking at differences.
- Magic squares have equal sums in all directions.
- Calendar blocks follow predictable sum patterns.
- Coding and decoding use reversible rules.
- Hexagonal numbers form a special sequence.
- Practise by creating your own patterns and magic squares.
- Pattern recognition helps in puzzles, tests, and everyday thinking.
