this post was submitted on 23 Sep 2024
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Unexpected Factorial
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When you use an exclamation mark with a number, you’re actually implying it’s not a normal number any more. It’s a factorial!
Ok, so how does this work?
5!=1×2×3×4×5=120
6!=720
These numbers get really large. For example:
15!≈1.3×10^12
So, next time you see a headline with 2000! in it, you’ll know what to expect.
There are also double factorials (n!!) and iterated factorials (n!)!, and they aren’t the same thing. Just add more exclamation marks and you get multifactorial. Check wikipedia to see how spicy it gets.
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Also, neat trick: If you need to add numbers higher than 10 you can take your shoes off to be able to do so.
Pfft, amateur hour. I count to eleven without taking my shoes off all the time.
Just not at my kid's school any more.
When lecturing I used to take my shoes off. I was asked about it once and said, which is true, it was because I was nervous and it helped my anxiety. But I should have used this as my reply.