# The Incredible Puzzle Thread

This is a thread to discuss some of your other favorite puzzles, riddles, brain teasers, armchair treasure hunts, etc.

To get started, here's an online puzzle hunt I've participated in before: Puzzlecrack. It's a week-long competition with clues given through the web page. Past competitions (and solutions) are still there for you to figure out.

Another similar one is Microsoft's College Puzzle Challenge.

Any other favorites?

-Klatuu

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## Comments

Harald B linked to graphic puzzles too, so I'm going to say it works.

I used to buy logic books. Kind of like crossword puzzle books, but with only logic stuff. My favourite ones were Logigraph (what you call Picross) and Logigram (stuff like the Einstein riddle).

There were some with numbers too. Not quite sudoku (that hadn't picked up in Europe yet) but the same kind of things. But my fav of all was logigraph for sure, logigram a close second.

Place them so the 2 smaller ones sit above the longer bottom one. Count the Hidden People.

Swap the positions of the top two pieces.

Count the Hidden People again.

Oh snap, I liked those as a kid too (well, if they're the ones I think you mean, with a grid of different elements).

I also half-love/half-hate Mindbenders-type stuff. In the ones we got the premise is almost always stupid, the answers sometimes obscure. Last time I was home for Christmas, the house was so crowded I ended up sharing my younger brothers' room, and we'd read these things out to each other for a while before actually going to sleep.

Or cheat and do it electronically!

... :eek:

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Is there a way to play without getting the solution before you even start? It kinda takes the fun of trying to guess what the picture is out of it.

Ha, it's way more fun to have the physical paper in front of you. Especially when you give it to kids to play with.

I buy one of those every now and then as well. One with picture cross only, as I grew tired of sudoku and kakuro a long time ago. Just laying on the couch with one of those is extremely relaxing when I need a break from my computer.

What's about, the only place in the world if you go 1 mile to the south, 1 mile to the east, and 1 mile to the north and come back to the exactly same point?

It's. The whole point is, when you are soooo used to resolve math problems, you start to came up with techniques. So, the normal math guy will start to came up with all the information he/she'll get before to actually see the problem.

All the maths problems, in Prof. Layton at least, are math problems you have to think differently than the normal math problems, and that's why those are difficult for the normal math student. Thank godness, I also draw, that's mean I have a certain part of the brain developed the normal engineer in my college does not. That helps, in some stuff.

I didn't realise she was just saying "20" in mathese (I didn't try to calculate it, to be fair, just looking at it makes me feel stupid).

If you were to calculate it, I'm sure there would at least be a square root involved somewhere.

Well, if they give us the length of AC and AB, you can use AD = sqrt(AC^2 + AB^2), which will me probably the first thing a math student will think off, except they will lack information. Also, you can use trigonometric stuff, if they give us the angle of DAC (let's say it alpha), because cos alpha = AB/AD, so AD = AB / cos alpha (you can use also sen alpha = AC/AD), but you are lacking information again.

In that moment a math student will saw the problem, figure out, and jump out of the window.

EDIT: by the way, my whole reasoning was "they only give us one number, and it's for something that doesn't even have a name. The thing kinda look like a circle. I'm gonna say it's one so the answer is 20".

So out of curiosity, how do you actually know that AB? and AC? are the same length? Is it because of the right angles?

It's a Rectangle, thanks to the right angles. If you separate them with AD, you get two Square Triangles. AB has the same lenght than CD, and AC has the same lenght than BD. Since you have an Square Triangle, you can use the Pythagorean Theorem to figure out AD, which is the hypotenuse, by using AB (or CD) and BD (Or AC). So, it's something like this:

=> (AD^2) = (AB^2) + (BD^2)

=> AD = sqrt(AB^2 + BD^2)

By the way, there's a way to figure out AC and AB if you suppose those are equal. Of course, by knowing AD = 20.

There are quite a few specific locations, but the answer you're looking for is the north pole

Now I'm curious for the other few specific locations!

When I said AB? and AC? I meant the ones that don't have names. Like, [AE] (the one with B on its way) and [AF] (the one with C on its way).

To know that [AD]=[AF], you need to know that [AE]=[AF], don't you?

My question was, how do you do that?

EDIT: Here, I changed the picture to show what I mean.

In my new picture, A isn't the center of the circle anymore.

In this case, it's obvious, since I wanted to show you what I meant. But how do you know that in the first picture, A is the center? What is the way to calculate it? Surely when you're just looking it's easy to get it wrong if it's just off the center, right?

In a equation, I can't think in a way to do it.

In fact, you can say there's no actual answer (For lack of information), because we're just assuming it's a quarter of a Circle. If it were the quarter of a Elipse, for example, AE =/= AF and we're screwed, unless they also give us AE.

So, in typical Math fashion, I assume it's a Quarter of a Circle. If it's a quarter of a circle, by definition all the lines from the middle to the perimeter of the circle has the same lenght (Because that's the definition of the circle). (I think). Since AF is a line from the middle to the perimeter, and AD is also a line from the middle to the perimeter, then AF = AD.

You then solve it geometrical.

That's a quarter of a Elipse! You screw me!

I totally forgot that, you right!

Grab a rule, measure the lenght of AF (Let's say it's 10 cm) and then measure the lenght of AD (Let's say it's 12 cm). Then you say:

10 cm -> 20 units

12 cm -> X units

Then x [units] = (12 [cm] * 20 [units]) / 10 [cm]

That's only works if the Drawing has the correct proportions. If it's not, we're screwed again.

Yes and no. If it's nobody telling you that's not a quarter of a circle, there's no reason I can't assume that, because it's nobody telling you either that drawing is correct at all. (That's always happen in a test the drawing are just demostrative, and normally you can't simple believe it's a circle because it's look like one.).

If we don't assume is a quarter of a circle, I cannot figure out a way to do it. And, if you want to know for sure it's a quarter of a circle, bad luck, because not always the drawings had the correct proportions. If you don't telling me that drawing had the correct proportions and it's not just demostrative of the example, I still can assume is a quarter of a circle, unless the problem itself tell me is not a quarter of a circle.

But, if the drawing has the correct proportions, you can use rule of three!

It has to do with the fact that terms like North, South, East, and West become undefined in specific locations. Consider if you were one mile north of the south pole; You'd go one mile south, there would be no east to travel (so you'd stand still) and then when you go one mile north, you could end up where you started- Or at an infinite number of other locations forming a circle 1 mile north of the pole.

Alternately, if you're willing to say that you *start out* heading N/S/E/W, then you can do some tricks with crossing the north pole and having the directions all change names.

Okay, a quarter of an ellipse then. I'm so math-challenged that I just thought it was a bigger circle and off-center >.>

Er, yeah, if I have a ruler I'll measure it directly and I'll know what size it is I was assuming you were supposed to calculate it.

I guess I'm just making things complicated. You just assume it's a quarter of a circle. Like I did.

I just was fairly sure math-people wouldn't just assume something like that without checking first in a more scientific way than their eyometre.

Here is an example, and I showed where the center is, too.

Are you sure? :O)

Yes.