Science Memes

11130 readers

2597 users here now

Welcome to c/science_memes @ Mander.xyz!

A place for majestic STEMLORD peacocking, as well as memes about the realities of working in a lab.

Rules

Don't throw mud. Behave like an intellectual and remember the human.
Keep it rooted (on topic).
No spam.
Infographics welcome, get schooled.

This is a science community. We use the Dawkins definition of meme.

Research Committee

[email protected]

Other Mander Communities

Science and Research

Biology and Life Sciences

Physical Sciences

Humanities and Social Sciences

Practical and Applied Sciences

Memes

Miscellaneous

founded 2 years ago

MODERATORS

[email protected]

682

And 299999999 is divisible by 13 (lemmy.world)

submitted 2 weeks ago by [email protected] to c/[email protected]

36 comments fedilink hide all child comments

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 22 points 2 weeks ago* (last edited 2 weeks ago) (1 children)

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.

[–] [email protected] 2 points 2 weeks ago* (last edited 2 weeks ago)

That is indeed an absurd amount of rules (specially for 7) !

It should be fun to develop each proof. Particularly the 1,3,2,-1,-3,-2 rule, which at first sight seems could be easily expanded to any other number.