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Cake day: August 15th, 2023

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  • Never realized there are so many rules for divisibility. This post fits in this category:

    Forming an alternating sum of blocks of three from right to left gives a multiple of 7

    299,999 would be 999 - 299 = 700 which is divisible by 7. And if we simply swap grouped digits to 999,299, it is also divisible by 7 since 299 - 999 = -700.

    And as for 13:

    Form the alternating sum of blocks of three from right to left. The result must be divisible by 13

    So we have 999 - 999 + 299 = 299.

    You can continue with other rules so we can then take this

    Add 4 times the last digit to the rest. The result must be divisible by 13.

    So for 299 it’s 29 + 9 * 4 = 65 which divides by 13. Pretty cool.






  • From article

    Reddit challenged its designation on the basis that it is mostly a text-based discussion platform, and links to videos uploaded elsewhere on the internet should not be factored in. The Irish regulator counter-argued that the audio-visual content on the platform is extensive, and pointed to its enormous reach, with 73 million daily users.

    Could not find any post statistics, but they probably are correct and percentage wise uploaded videos should be at the bottom, but total count probably is too large to be simply disregarded. Reddit probably has more videos than Vimeo which is purely video based. And if Reddit would be in the clear then so should be Twitter and Facebook since those too are primarily text based.