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Digital Roots
Last updated at January 8, 2026 by Teachoo
Class 8 (Ganita Prakash - 1, 2 & Old NCERT)
Chapter 5 Class 8 - Number Play (Ganita Prakash)
- Sum of Consecutive Numbers
- Parity of Arithmetic & Algebraic Expressions
- Pairs to Make Fours
- Factors and Multiples
- Always, Sometimes, or Never
- What Remains?
- Figure it out - Page 122, 123
- Divisibility Rules - 2, 5, 10 and 3
- Shortcut for Divisibility by 9
- Figure it out - Page 126
- Shortcut for Divisibility by 11
- Divisibility Shortcuts for Other Numbers
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Digital Roots
- Figure it out - Page 131
- Digits in Disguise
- Figure it out - Page 132, 133, 134
Transcript
Digital RootsTo find the digital root, you just add the digits of a number. If the answer has more than one digit, you add those digits together again. You keep doing this until you are left with just one digit. Example: Let's take the number 489,710. Add the digits: 4 + 8 + 9 + 7 + 1 + 0 = 29 29 is two digits, so add them again: 2 + 9 = 11 11 is still two digits, so add them again: 1 + 1 = 2 ∴ The Digital Root is 2. Now, we have a question from the book What property do you think this digital root will have? Recall divisibility shortcut for 9. The digital root of a number tells you the remainder when that number is divided by 9. If the digital root is 9, the number is perfectly divisible by 9. If the digital root is 5, the remainder when dividing by 9 is 5. We can check this for number 17 Digital root for 17 is Sum of digits = 1 + 7 = 8 ∴ Digital root is 8 And, when dividing by 9 17 ÷ 9 gives remainder 8
