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Question 3 - Figure it out - Page 131 - Chapter 5 Class 8 - Number Play (Ganita Prakash)
Last updated at January 8, 2026 by Teachoo
Figure it out - Page 131
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
- Digital Roots
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Figure it out - Page 131
- Digits in Disguise
- Figure it out - Page 132, 133, 134
Transcript
Question 3 What will be the digital root of the number 9a + 36b + 13?Any number multiplied by 9 (like 9a) always has a digital root of 9. Example: 27 has digital root = 2 + 7 = 9 Any number multiplied by 36 (like 36b) also has a digital root of 9 Example: 72 has digital root = 7 + 2 = 9 Because 36 is a multiple of 9 Thus, we can sat that Multiples of 9 don't change the digital root when you add them (it's like adding 0 in this magic math). So, we only need to look at the 13. Digital root of 13 is 1 + 3 = 4. Answer: The digital root is 4.
