Number Play — Class 7 Mathematics

This playful chapter explores numbers through puzzles, parity, grids and famous sequences. Parity is the property of being even or odd: even numbers can be paired with no leftover, odd numbers cannot. You learn rules such as even + even = even, odd + odd = even, even + odd = odd, and use them to decide quickly whether a situation is possible (five odd cards can never sum to the even number 30). Expressions can be designed to be always even , always odd , or either. You then build magic squares — grids where every row, column and diagonal share the same magic sum (for the numbers 1–9 the magic sum is 15 and the centre must be 5) — and generalise their structure with a centre letter . The chapter celebrates the Virahanka–Fibonacci sequence , where each term is the sum of the previous two, discovered in Indian poetry centuries before Fibonacci. It ends with cryptarithms, puzzles where letters replace digits.