Revision Notes for Class 7 Maths Chapter 6: Number Play

Quick revision notes summarizing all key concepts from Class 7 Maths Chapter 6 “Number Play”. These Class 7 Mathematics Chapter 6 notes are ideal for quick revision just before exams.

Last Updated: September 23, 2026

• Parity refers to whether a number is odd or even.
• Sum rules: Even+Even=Even, Odd+Odd=Even, Even+Odd=Odd. Subtraction follows the same rules as addition for parity purposes.
• An odd count of odd numbers sums to odd; an even count of odd numbers sums to even. Any count of even numbers always sums to even.
• Product parity: a product is even if at least one factor is even; a product is odd only if both factors are odd.
• All even numbers can be written as 2n; all odd numbers can be written as 2n − 1 (n = 1, 2, 3, …).
• A classic 3×3 magic square using numbers 1–9 has magic sum 15 and is unique up to rotation/reflection (8 total variations). For a magic square with centre value m, every row/column/diagonal sums to 3m.
• Adding a constant c to every cell of a magic square increases the magic sum by 3c; multiplying every cell by k multiplies the magic sum by k.
• The Chautisa Yantra is a famous 10th-century 4×4 magic square from Khajuraho with magic sum 34, where even the four corners, four central cells, and any 2×2 block sum to 34.
• The Virahanka-Fibonacci sequence (1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …) is formed by adding the two previous terms; its parity repeats in a 3-term cycle: odd, odd, even.
• The number of ways to write n as an ordered sum of 1s and 2s equals the Virahanka term for n (e.g., 6 can be written in 13 ways).
• Cryptarithms are puzzles where letters represent digits in an arithmetic equation; solve them using place-value reasoning and testing constraints systematically.

NCERT Solutions: Class 7 Maths Chapter 6
Extra Questions: Class 7 Maths Chapter 6

For the full chapter, see the Class 7 Maths book page and the Class 7 Maths Formulas Handbook.

Frequently Asked Questions

What is a prime number, and how is it different from a composite number?
A prime number has exactly two factors, 1 and itself, while a composite number has more than two factors, meaning it can be divided evenly by at least one number other than 1 and itself.

What is the significance of the Highest Common Factor and Lowest Common Multiple of two numbers?
The Highest Common Factor is the largest number that divides both numbers exactly, useful for simplifying fractions, while the Lowest Common Multiple is the smallest number both numbers divide into exactly, useful for comparing fractions.

Written by Satish

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