Does that hold for every base, where the divisor is 1 less than the base?
Specifically hexidecimal - could it be that 5 and 3 have the same “sum digits, get divisibility” property, since 15 (=3*5) is one less than the base number 16?
Like 2D16 is16*2+13 = 45, which is divisible by 3 and 5.
Can I make this into a party trick?! “Give me a number in hexidecimal, and I’ll tell you if it’s divisible by 10.”
Am thinking it’s 2 steps:
Does it end with a 0, 2, 4, 6, 8, A, C, E? Yes means divisible by 2.
Do the digits add up to a multiple of 5 (ok to subtract 5 liberally while adding)? Skip A and F. For B add 1; C->2, D->3, E->4. If the sum is divisible by 5, then original number is too.
So if 1 and 2 are “yes”, it’s divisible by 10.
E.g.
DEADBAE16 (=23349547010): (1) ends with E, ok. (2) 3+4+3+1+4=15, divisible by 5. Both are true so yes, divisible by 10.
C4744416 (=1287482010): (1) ends with 4, ok. (2) 2+4+7+4+4+4=25, ok.
BEEFFACE16 (=3203398350): (1) E, ok. (2) 1+4+4+2+4=15, ok.
Is this actually true? Have I found a new party trick for myself? How would I even know if this is correct?
Ron Swanson meme where he says “I’m a simple man”. He’s looking at the camera, in a brown suit, with a sexy mustache and very slight smirk. Background is blurry paintings. Caption says “I’m a simple man” at the top and “I see a reply, I upvote it” at the bottom. End description.
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Ron Swanson meme where he says “I’m a simple man”. He’s looking at the camera, in a brown suit, with a sexy mustache and very slight smirk. Background is blurry paintings. Caption says “I’m a simple man” at the top and “I see a reply, I upvote it” at the bottom. End description.