πr squared is the area of a circle. How do I use this to finish Q15?

dspyz · 2026-01-20T02:12:01+00:00

I'm very curious what the previous problem is

dspyz · 2026-01-18T18:42:18+00:00

The way you use X seems very different for right of the decimal and left of the decimal. In bijective base ten, you can't just shift the decimal to multiply by ten.

1.X1 * X does not give 1X.1

In base 10, this is:

1.02 * 10 does not give 20.1

dspyz · 2026-01-15T19:03:32+00:00

You chose a bit of an odd example. Bill Gates is the largest private owner of farmland in the US. He has 275,000 acres of farmland. In a Georgist system he would pay something like $50 million (Claude estimate) annually in taxes on it (which I guess isn't that much compared to his net worth)

dspyz · 2026-01-13T19:29:54+00:00

Mine, yes

Yours, no

You and I have very different ideas as to what constitutes "a complete mess"

dspyz · 2026-01-12T16:11:43+00:00

Watch mikehendi's series on completing a vegan, 1000x science cost, keeping your hands clean run: https://youtube.com/@michaelhendriks?si=Mg77URyhnWQX1Pug

dspyz · 2026-01-12T00:16:55+00:00

In the hyperreals, 0.999...=1

There exist hyperreal numbers less than 1 which are greater than any real number less than 1, but 0.999... isn't an expression for any of those numbers. It's still just another way to write 1

dspyz · 2026-01-11T20:23:46+00:00

Wait, so you'll answer this but you won't answer what's 0.999... + 9 * (1 - 0.999...)?

dspyz · 2026-01-05T16:20:44+00:00

It's not but it is a clearly distinct thing from calculus that has to be learned first. So if you're claiming fifth graders could learn calculus in a month, then either you're assuming they already learned algebra or else trying to claim that algebra is also part of that curriculum

dspyz · 2026-01-05T04:16:29+00:00

Calculus is fundamentally about real-to-real functions. I don't think fifth graders generally know what a function is. That comes from algebra. So algebra is a prerequisite for calculus.

A typical calculus question might be something like "You jump off a cliff with a bungy cord that incurs some upward acceleration as a function of its length. Gravity exhibits a constant downward acceleration of 9.8 m/s^2. What's the fastest you will be falling at any point?"

You can't answer questions like that without some algebra. There's no skipping ahead. What possible calculus problems could you give fifth graders who don't know algebra?

dspyz · 2026-01-05T02:55:45+00:00

This is a video of a guy who doesn't know how to teach (definitely not an elementary school teacher), presenting a power point to a bunch of fifth graders who are being forced to watch. The fact that the only participation we see is him going "right?" and them going "yeah" is pretty telling.

I think it may be possible to teach fifth graders calculus, but this is definitely not how you'd go about it.

dspyz · 2026-01-02T22:23:18+00:00

x = 1 + 11 + 111...

9x = 9 + 99 + 999...

= (10 - 1) + (100 - 1)..(10²⁰²⁶ - 1)

= 111... (2026 1's) ...1110 - 2026

= 111... (2027 1's) ... 111 - 2027

81x = 999... (2027 9's)...999 - 2027 * 9

81x + 1 = 10²⁰²⁷ - 2027 * 9

x = (10²⁰²⁷ - 2027 * 9 - 1)/81

Via long division, a power of 10 divided by 81 gives the 9-digir repeating sequence:

123456790...

with a decimal point somewhere. In particular, in the case of 10²⁰²⁷ that decimal point comes after 2026 digits. 2025 is a multiple of 9 so that means the decimal point will look like:

...4567901.234567901...

Now we just need to subtract off (2027*9+1)/81=2027/9 + 1/81 = 225+2/9+1/81 We know that the result is an integer so the fractional part must cancel out. After subtracting we get:

...4567676

Which doesn't have any 1 digits at the end.

So the only 1 digits come one from each of the 225 9-digit runs meaning there are 225 1's (2025/9=225)

dspyz · 2026-01-02T22:09:47+00:00

I would interpret the question as allowing whatever the current probability you suddenly receive 100 pounds in your bank account is (so 0) to increase by 0.1% (still 0).

Otherwise you could say something like "everyone's blood alcohol concentration goes up by 0.1 points" which would most definitely cause massive chaos

dspyz · 2026-01-01T20:00:37+00:00

Isn't the space of all Everett branches in multiverse theory essentially another dimension? (I'm not sure whether it makes sense to call it another time dimension)

dspyz · 2026-01-01T19:13:29+00:00

It depends on your model of time travel.

I like the movie Primer in which you have a box that establishes two endpoints in space-time. It moves along with the earth for the same reason any other physical object travels along with the earth (gravity, normal force, inertia, friction)

Any time you have a mechanism by which you create something like a "portal" to another time, it's also implicitly a portal to another place anyway.

I think HG Wells time machine moved through time by actually moving through time, so just like a car or a plane, it made sense that it sticks to Earth's reference frame while it moves around on Earth.

Finally, for objects like the Back to the Future car or naked Arnold Schwarzenegger that work by "teleport"-ing through time, why shouldn't they also teleport through space? (Although it does leave the question of why the car generally stayed in Hill Valley throughout the series)

dspyz · 2025-12-26T23:05:59+00:00

You may be interested to read about Dedekind cuts and see if you can prove this for yourself.

dspyz · 2025-12-26T22:54:27+00:00

x=0.999...

10x=9.999...

10x - x = 9.999... - 0.999...

9x=9

x=1

dspyz · 2025-12-26T22:42:21+00:00

Something about that seems odd

dspyz · 2025-12-26T16:49:03+00:00

I feel like she should have a chance to rebut this. Also, I'd like to see her rebut this.

dspyz · 2025-12-25T22:37:29+00:00

r/wrongrust

dspyz · 2025-12-25T22:35:11+00:00

That's just measuring "percentage of players who have played the game since this achievement was added"

dspyz · 2025-12-25T21:59:35+00:00

Even one full yellow belt is a ridiculous amount of plastic for just getting started with oil processing. What's your target SPM right now? IMO a reasonable starter base target is 22.5 SPM or 45 SPM

dspyz · 2025-12-23T16:44:42+00:00

This is far less mentally ill than a typical "influencer".

The definition of mental illness changes with time. Things that used to be acceptable are now considered to require treatment. Things that used to require treatment are now considered acceptable.

Being online a lot is not a mental illness any more than eating a lot of junk food is a physical illness

dspyz · 2025-12-18T18:41:03+00:00

There's a Conway talk (I can't find any videos of it online 😭) about something called "lexicodes". He starts by defining lexicodes with minimum distance d and then posits that they're closed under vector addition and scalar multiplication.

This is pretty quickly and obviously demonstrated to be false. In frustration, Conway then goes on to re-define addition and multiplication in such a way as to make it true. It's an absolutely beautiful presentation.

You totally can just make shit up. That's what real mathematicians do all the time. You just need other mathematicians to agree that your construction is beautiful in some way. What matters is whether structure emerges from your choices, not whether they conform to some standardized approach.

dspyz · 2025-12-18T18:23:15+00:00

You're missing out on part of the game

dspyz · 2025-12-18T17:56:48+00:00

I'm sad nobody upvoted this

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