• beckerist@lemmy.world
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    1 year ago

    7 is double the last number and subtract from the rest

    749 (easily divisible by 7 but for example sake)

    9*2=18

    74-18=56

    6*2=12

    5-12= -7, or if you recognize 56 is 7*8…


    I’ll do another, random 6 digit number appear!

    59271

    1*2=2

    5927-2=5925

    5*2=10

    592-10=582

    2*2=4

    58-4=54, or not divisible

    I guess for this to work you should at least know the first 10 times tables…