• rbos@lemmy.ca
    link
    fedilink
    English
    arrow-up
    3
    arrow-down
    2
    ·
    4 hours ago

    This hurts my brain. Why do we care about all the weird fractions? +/- 0.1 is just another way of saying 1/10. You can still do that if you want without having to do fraction math in random denominators.

    • ryathal@sh.itjust.works
      link
      fedilink
      arrow-up
      1
      ·
      2 hours ago

      The fraction allows you to communicate length and tolerance in a single number. A decimal implies precision to the last number, a measure with a fraction can show 1/8 as more granular than 1/16. 1/8 of a cm is less precise than a mm, but if you wrote 1.125 cm, you are now implying sub mm level precision.

      This matters because the level needed in building generally doesn’t line up to 1/10 measurements. For example if you had a brick wall and a row had 1 cm height differences between bricks in a row it would be extremely obvious and look terrible. A 1mm height difference would be impossible to notice, but is also overkill to get that level. Ideal is about 5/8 cm or 6.35 mm difference over 3 meters of wall. The fractional measure often ends up easier to work with in practice.