Schooling · Class 6 · Mathematics · Number Play · Chapter on a page
CBSE Class 6 · Mathematics · NCERT Ganita Prakash
Number Play: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 26 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
This note's current text has no applied fact-check on record.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- Digit
- You can reverse a number by writing…
- Adding a two-digit number to its…
- Palindrome
- Multiplying certain numbers by 9…
- The sum of digits of a number can…
- Playing with place value (ones…
- Formulas and facts
- Reverse of a two-digit number
- Sum of a two-digit number and its…
- Divisibility by 9
- Divisibility by 3
- Palindrome check
- Watch out for
- Confusing the reverse of a number…
- Thinking all numbers become…
- Forgetting that a single-digit…
- Adding digits wrongly when checking…
- Believing number patterns always…
What this chapter is about
This chapter is all about having fun with numbers while discovering interesting patterns and properties. You already know how to add, subtract, multiply and divide. Now you will look at numbers in new ways — finding patterns in digits, playing games with numbers, and noticing how numbers behave in surprising situations.
Key ideas
- Digit means each single symbol in a number. The number 435 has three digits: 4, 3 and 5.
- You can reverse a number by writing its digits in the opposite order. The reverse of 123 is 321.
- Adding a two-digit number to its reverse often gives interesting results. For example, 25 + 52 = 77.
- Palindrome means a number that reads the same forwards and backwards. Examples: 11, 121, 4554.
- Multiplying certain numbers by 9 creates patterns in the digits of the answer.
- The sum of digits of a number can tell you things about that number, like whether it is divisible by 3 or 9.
- Playing with place value (ones, tens, hundreds) helps explain why number tricks work.
- Number patterns often repeat, and spotting them helps you predict what comes next.
Formulas and facts to remember
- Reverse of a two-digit number: If a number is written as (10 × a) + b, its reverse is (10 × b) + a. Here a is the tens digit and b is the ones digit.
- Sum of a two-digit number and its reverse: The answer is always 11 × (a + b). That is why results like 77, 99, 121 appear often.
- Divisibility by 9: If the sum of all digits of a number is divisible by 9, then the number itself is divisible by 9.
- Divisibility by 3: If the sum of all digits is divisible by 3, the number is divisible by 3.
- Palindrome check: Read the number from left to right and right to left. If both readings are the same, it is a palindrome.
Common mistakes
- Confusing the reverse of a number with subtracting from it → Reversing means flipping the order of digits, not doing any arithmetic.
- Thinking all numbers become palindromes after one addition with their reverse → Some numbers need several steps of adding and reversing before they become palindromes.
- Forgetting that a single-digit number is always a palindrome → Numbers like 5 or 7 read the same both ways.
- Adding digits wrongly when checking divisibility → Take your time; add each digit carefully, one by one.
- Believing number patterns always continue forever → Some patterns break after a few steps; always check.
Quick revision
- The reverse of 47 is 74. Adding them gives 121, a palindrome.
- A palindrome reads the same forwards and backwards.
- Sum of digits trick: add all digits to check divisibility by 3 or 9.
- Two-digit number plus its reverse always equals 11 times the sum of its digits.
- Look for patterns — they make big calculations easier.