Once Geniusbeauty was asked:

– Why are you called **Geniusbeauty**? I see you’re **beautiful**, but why “**Genius**“? I’ve got a **riddle** for you, so if you **solve** it, you will prove me, that you are the real **Geniusbeauty**. Here is a heap of **bricks**. I’ll give you a slide **rule** and you will have to measure the **diagonal** of the brick. But remember, that you can **measure** it only once!

In the end she proved, that she was not only **beautiful**, but also **smart**. How did she do this? What did she **answer**?

Please, if you want to find the solution yourself, do not look at the comments of this post, because someone could have already written it there. You will find the solution in the next brain game. You are always welcome to ask questions about the task, in case something is not clear. But sorry, I will not answer leading questions. Good luck!

The answer to the previous brain game is:

4 9 2

3 5 7

8 1 6

Every row, column and diagonal is 15. If you rotate the grid, the logic stays the same. For those, who would like to find out the logic in detail, here is the link: http://en.wikipedia.org/wiki/Magic_square.

Congratulations to those, who solved it: Stargoat, Chris, Steve, Hj, Laurentiu Craciunas, Jed Hawk! Many thanks to Jed Hawk for the detailed explanation.

Hi Geniusbeauty I e-mailed you what I believe is the correct answer. Interesting little puzzle.

Here’s my solution – you don’t need to post this, but I didn’t see

a link to email you rather than posting.

I assume by “heap” that there are at least three bricks. Create a

“mini-step” by putting one brick in front of you, and stacking two

bricks directly in back of it. Now measure from the top-front-left

corner of the first brick to the top-right-back corner of the top brick

of the two in the back. Essentially you are measuring the diagonal

of where a fourth brick would be if you had created two stacks of two bricks.

Alternate solution: If “measure once” means you are only allowed to use

the rule once (position it once), but can read off multiple numbers, there’s

another solution. Position three bricks next to each as in this ASCII diagram

(hopefully this won’t get clobbered in transmission), but without any gaps

between bricks. Basically from the width of the edge facing you

is different for each brick.

|—| |—–|

| | | |

———- | | | |

| | | | | |

———- |—| |—–|

Now place the ruler across the bottom, reading the numbers where each

brick ends. You can now compute the length of each edge, and use

the Pythagorean theorem to compute the diagonal. This isn’t as nice

a solution. Even though you’re placing the ruler once, reading

three numbers violates the spirit of “using” it once.

measure it from corner to corner. Unless you want to use a worthless formula. That was easy.

And how, darius, do you get the ruler through the brick to do that

measurement? Diagonal in this problem means front-left-top corner

to rear-right-back corner (or one of the other three equivalents), not

the diagonal of a face.

I’m thinking of using mirrors but can’t quite come up with what I want.

Mathematically, if the brick has dimensions L, B and H. Then the length of the true diagonal is:

sqrt(L^2 + B^2 + H^2).

I need some way to organise the mirrors in a single plane, possibly on the same parallel plane as the base of the brick, that allows me to measure one line only.

Maybe, since the flat diagonal = L^2 + B^2 I could line that up against the H side, somehow. Thus only need the mirror for the Height of the brick but argh, I could be wrong anyway.

Want a hint Jed? If not, stop reading.

If the brick wasn’t there, you could easily measure its diagonal.

I didn’t read the word “heap” the first time rounds – oops, that’ll teach me. I assume that every brick is uniform then, from the same mould so to speak.

Well in that case you can rest two bricks and measure in one straight line, by positioning the height of the second brick to extend the flat diagonal of the base of the first brick.

A—-B

C—-D

E

F

This one can be done in a hard/math way and in a genius way, so here’s the genius way đ

Get 3 bricks, put them one near another and measure the distance between the lower right corner of the left brick to the upper left corner of the right brick. This way you’ll find the diagonal of the middle brick. Here’s a quick painting: http://img137.imageshack.us/img137/8402/caramiziwd1.gif