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 estherchaya | |
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received this in an email today: 1. Grab a calculator (you won't be able to do this one in your head) (first of all, let me say I'm insulted by that. I tried and I did this in my head without any problem, though it certainly took longer)2. Key in the first three digits of your phone number (NOT the area code) (second, let me say this is also ridiculous. It works fine with the area code. It's just a less interesting answer)3. Multiply by 80 4. Add 1 5. Multiply by 250 6. Add the last 4 digits of your phone number 7. Add the last 4 digits of your phone number again. 8. Subtract 250 9. Divide number by 2 Do you recognize the answer? So yeah, it's cool. And I'll never figure out how people work these things out. I've tried to create similar "tricks" but have never been able to do it. It irritates me that other people are so much smarter than me, and it's unfair that it irritates me. I should get over myself. I'm not all that, and I know that, I just wish I were! :) Tags: geekery, math
Current Mood:  awake
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From: xiphias |
Date:
August 26th, 2005 01:17 pm (UTC)
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Yeah, like a lot of people, my reaction to these is to write down the algebra, simplify the equation, and then plug in the values. That takes a lot of the mistery out of it.
I mean, I look at that, and see: ((250(80x + 1) + y + y) - 250) / 2
Which is, obviously, (20,000x + 250 + 2y - 250) / 2
Which is 10,000 x + y.
All you need to do is figure out what result you want, put it into algebra, and then stick in a bunch of weird stuff that all cancels out.
Actually, that kind of sounds like fun. Wanna make one up right now?
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I did the general case in my head as I read it; I've seen a lot of these and this was one of the easiest ones I've come across.
The ones I saw as a kid often constructed your age from your birthdate or vice-versa (but hidden in some other stuff that got added in and taken back out).
I remember a smart friend (but not so used to puzzles) being totally befuddled by a somewhat more clever one (it actually appears to be mind-reading, since it seems it couldn't possibly know the last thing you have to make up). Until I explained it. It performs a set of operations on a number that you start with, gets you to turn the answer into a letter, to think of a country starting with that letter, an animal starting with the second letter of the country name and then think of the colour of the animal, whereupon it tells you the colour you're thinking of. I imagine you've seen that one.
But in that case the sequence of operations takes any number to one of two possible results, and then treats those two differently, so that they both end up at 4. So you always choose a country starting with D, for which almost everyone says Denmark (why not "Djibouti"?), then Elephant (what about Elk? Emu? Ermine? Eel? Euro?). So they almost all end up at "Grey".
In general the more usual ones just rely on doing and then undoing the same simple operations (add, subtract, multiply, divide), with nothing much else going on. I've always thought that it might be worth creating one that's actually subtle. There are some really neat tricks you can put in that make it seem absolutely impossible to know what the outcome might be. One day, maybe, I'll have some time on my hands and make one where people with good algebra might still say "How the hell can that possibly work?".
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