- [[2024-08-12 10:38:54+00:00]] @[[flancian@social.coop]] (<a href='https://social.coop/@flancian/112948617827679033'>link</a>):
  - <p>I saw this number on the floor on a discarded receipt in the train station: [[3493]]</p><p>It's a multiple of seven. Proof:</p><p>349 - 6 = 343 (subtracting double the last digit from the rest of the number)<br>34 - 6 = 28 (again, reaching a multiple of seven)</p><p>Thanks universe for providing a nice example/practice session for a recently learnt divisibility rule :)</p><p>On closer inspection, it's even simpler to verify: 3500 clearly is a multiple of seven, and the number is 3500 - 7.</p>