Art of Wiping Butt

How do you wipe your butt?

This question has bugged me for ages, and I was just thinking about it today while wiping my butt, and thought I would blog about it =D

I think it’s one of those things that you think everyone does it the same way as you do, but in reality probably not.

It’s a bit of a dark art because people don’t generally talk about it. It’s like a family thing. Parents teach children, children teach grandchildren… etc. I imagine after so many generations, different families must have developed very different ways of wiping butt.

Want to know if your ancestors came from Africa? No problem! Just go watch them wipe their butts.

On a more serious note, if everyone does it a different way, by definition, most people aren’t doing it in the optimal way.

I think the most important choice in butt wiping is how many sheets of toilet paper to begin with, and how to fold.

I always fold by half every time. This is not the most efficient use of toilet paper, but I find it difficult to just fold part of it, because to only fold part of it, you’ll have to wipe off-center (of the strip of toilet paper), and if the water level is high, the longer end can dip into the water. That is gross.

So I fold by half.

For the number of sheets, I’ve always used 4 until a few years ago, then I switched to 3. I think 3 is better because when you fold by half, there will be no crack in the middle. So it doesn’t rip as easily.

But is that optimal? let’s find out.

If we assume I can do a last wipe with an area of a half sheet of TP, and I start after one fold (to make it thicker), the number of wipes I can do with n sheets is –

e1

and the average number of wipes per sheet, r, is

e2

and the derivative

e4

And we have the local maximum –
e5
(!!!)

That means, if we round it to whole sheets, the most efficient way is to take one sheet every time, and use it once! That’s a ratio of 1 wipe per sheet.

Which makes sense.

If we take the 3 sheets example, we get first wipe at 1.5 sheets, second wipe at 0.75 sheets, then we are done. That’s 0.66 wipes per sheet. For 4 sheets it’s 0.75 wipes per sheet. But obviously it will only go down from there on, since it’s logarithmic.

I should try it out. 1 sheet at a time.

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