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Digits in Disguise
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
- Digital Roots
- Figure it out - Page 131
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Digits in Disguise
- Figure it out - Page 132, 133, 134
Transcript
Digits in Disguise (Cryptarithms)Cryptarithms are puzzles where numbers is replaced by a Digit Example: Let’s solve some Cryptarithms Solve We can do this by checking multiple digits Step 1 - Checking unit digit 1 + B = 0 This is only possible if B = 9 Step 2 - Checking Ten’s Digit Carrying 1 from 1 + B, we have 1 + A + 1 = B Putting B = 9 1 + A + 1 = 9 2 + A = 9 A = 9 – 2 A = 7 Thus, A = 7, B = 9
