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Joined 1 year ago
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Cake day: June 26th, 2023

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  • Same, using Chat GPT 4. It explained the steps without prompting, which is different from the single line answer shown in the post too. I got this…

    Let’s break this down step by step:

    1. Sally has 3 brothers.
    2. Each of those brothers has 2 sisters.

    Sally is one of those sisters for each of her 3 brothers. Therefore, the second sister that each brother has would be the same other sister.

    This means that Sally has only 1 other sister, making a total of 2 sisters in the family (including Sally herself).

    So, Sally has 1 sister.




  • That one’s actually really easy to prove numerically.

    Not going to type out a full proof here, but here’s an example.

    Let’s look at a two digit number for simplicity. You can write any two digit number as 10*a+b, where a and b are the first and second digits respectively.

    E.g. 72 is 10 * 7 + 2. And 10 is just 9+1, so in this case it becomes 72=(9 * 7)+7+2

    We know 9 * 7 is divisible by 3 as it’s just 3 * 3 * 7. Then if the number we add on (7 and 2) also sum to a multiple of 3, then we know the entire number is a multiple of 3.

    You can then extend that to larger numbers as 100 is 99+1 and 99 is divisible by 3, and so on.