DS when negative

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  • #5107
    Marco de Hevia
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    What happens when the substraction of the DSs is negative?

    Ex: 21 – 14 = 7

    DS: 3 – 5 = -2

    #5109
    Ofpad
    Participant
    • Topics: 0
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    Hi Marco,

    Thank you for asking this question and I am not sure how I missed adding this in the lecture. When the subtraction of the DS is negative you add 9 to the negative number.

    21 – 14 = 7

    3 – 5 = -2 (+9) = 7.

    Another example

    24 – 7 = 17

    6 – 7 = -1 (+9) = 8 (Which is the digit sum of 17 = 1 + 7 = 8)

    Thank you for asking this question. Will update the lecture so its more clear. 🙂

    Hope this clarifies.

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