CBSE Class 6 — Notes, Chapters & Practice Quizzes

Chapter 3: Number Play

Summary

This chapter explores numbers through games, puzzles and patterns, building computational thinking. It opens with a line of children each saying the number of taller neighbours they have, showing how numbers convey information. Supercells are cells whose number is larger than all neighbouring cells; students fill grids to maximise supercells. The chapter places large numbers on number lines and counts how many 1-, 2-, 3-, 4- and 5-digit numbers exist (\(9, 90, 900, 9000, 90000\)). It studies digit sums, palindromes (numbers that read the same both ways, such as 575 or 12321), and the reverse-and-add method. A highlight is the Kaprekar constant: repeatedly making the largest minus the smallest number from a 4-digit number always reaches 6174. Clock and calendar number patterns, mental-math methods, and number-pattern sums are covered. The famous unsolved Collatz conjecture is introduced \u2014 halving even numbers and applying \(3n+1\) to odd numbers always seems to reach 1. The chapter ends with simple estimation and winning strategies for number games like reaching 21.

Key terms

Important questions

Think about various situations where we use numbers.

Try answering the questions below and share your reasoning.

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Complete Table 2 with 5-digit numbers whose digits are ‘1’, ‘0’, ‘6’, ‘3’, and ‘9’ in some order. Only a coloured cell should have a number greater than all its neighbours.

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Find out how many numbers have two digits, three digits, four digits, and five digits.

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Digit Detectives

Write all possible 3-digit palindromes using these digits.

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Puzzle time

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