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Coded message brainteaser

By David, 21 March 2018 Brainteaser

You’ve just received a secret coded message:

AD, BA, BH, CE, DB, DI, EF

You know it follows a pattern, but can you work out what pair of letters come next?
  
Scroll down for the answer!

 

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Brainteaser answer

You might have noticed that the first letter in each term is further along the alphabet. This could be considered a clue. And what if the pairs of letters represented numbers?

You can convert the letters to numbers using a simple substitution cypher:

A = 1, B = 2, C = 3 and so on.

This gives us the sequence:

14, 21, 28, 35, 42, 49, 56

You might notice that they’re all multiples of seven! That means the next number in the sequence is 63.

Taking it back through the substitution code, we get the answer, FC.

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4 comments

  1. I did it differently but still got it, as the number of letters for the first one goes 1, 2,1,2,1 and goes up A,b,c etc. while the second letter in each increase by one letter. The letters that have one letter so the A,C and E have the second letter D,E,F so goes up one while the two numbers go up in the same order but start at A and H and therefore when you get to the next one in the order it is FC.

      Reply
    1. That’s a clever pattern! It might reveal something special about the seven times table. Have you tried extending the pattern even further? does it still make sense?

        Reply
  2. What a great code challenge for us to do over lunch!

      Reply
  3. I looked into the pattern further and it holds up.
    AD 14
    BA 21
    BH 28
    CE 35
    DB 42
    DI 49
    EF 56
    FC 63
    FJ 70
    GG 77
    HD 84
    HK 91
    IH 98
    JE 105
    JL 112
    KI 119
    LF 126
    LM 133
    MJ 140
    NG 147
    NN 154
    OK 161
    PH 168
    PO 175
    QL 182
    RI 189
    RP 196

    I’m not sure as to why it works for all the letters but would be interesting to find out why it does that. Do you have any ideas?

      Reply

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