Chap 5 Algebra... Recap the Crystal Ball Mystery

1 comment:

  1. Dear S1-01

    We have 'decoded' the mystery behind the crystal ball in class.
    Here's the explanation.

    Let the 2 digits be x and y
    In other words, the 2-digit number we have can be expressed as 10x + y

    Now, the sum of 2 digits would be x + y

    Subtracting the sum from the original number,
    10x + y - (x + y)
    = 10x + y - x - y
    = 9x
    Hence, resulting a number that is a multiple of 9.

    Therefore, what the system needs to do is to generate a symbol that appears in positions that are multiples of 9 (e.g. 9th position, 18th position, 27 position, etc)