<!--
.. title: everything looks like a π
.. slug: everything-looks-like-a-π
.. date: 2025-07-01 19:25:28 UTC-05:00
.. tags: math, nerd, youtube
.. category: math
.. description: In which Youtube abuses infinite sums.
.. type: text
.. has_math: true
-->

Here's a cute little computation.  Suppose you pick two uniform random
numbers.  What's the probability that their ratio rounds to an even
number?
It's straightforward enough to get "this is a sum that looks like it's
probably famous."  But it turns out that different definitions of
rounding pull in different transcendental constants.

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The spoilery answer that, if you round to the *nearest* integer, you
get probability $\frac{5-\pi}{4} \approx 0.46$.  But if you *floor*
to an integer, you get $1-\frac{\ln 2}{2} \approx 0.65$.

It's kind of wild that, of all the uncountable transcendental numbers,
the sorts of problems we build tend to generate just the same handful
of them.
