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Comment on Panik

letsgo@lemm.ee ⁨1⁩ ⁨year⁩ ago

There are tricks like that for a lot of numbers. For 7, chop off the last digit, double it and add it to what’s left. Repeat as required. If the result is divisible by 7 then the original number was. eg: 356 -> 35+12=47 not db7. 357 =>35+14 both db7 so we don’t even need to do the add.

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Dagwood222@lemm.ee ⁨1⁩ ⁨year⁩ ago
Clever.

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- Klear@sh.itjust.works ⁨1⁩ ⁨year⁩ ago
  Girl.
  
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BruceDoh@sh.itjust.works ⁨1⁩ ⁨year⁩ ago
14: 1 + 8 = 7. Not db7

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- sockenklaus@sh.itjust.works ⁨1⁩ ⁨year⁩ ago
  You clearly mean:
  
  14: 1 + 8 = 9 (not db 7)
  
  Someone else in this thread correctly stated:
  
  “Chop of last digit, double it and subtract from what is left”
  
  14: 1 - 8 = -7. (dB 7!)
  
  Math is awesome, I didn’t know this trick!
  
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  - BruceDoh@sh.itjust.works ⁨1⁩ ⁨year⁩ ago
    Yes, that’s what I meant. The subtract rule works.
    
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