Sunday, January 15, 2006

Amazing Puzzles

Ok, so I'm easily fooled and relatively gullible, but these two puzzles had me (happily and infuriatingly) stumped for ages. See how you honestly fare:

Mind Reader
This is a well known and clever little trick by Andy Naughton.

Below is an explanation of how the Flash Mind Reader works. If you want to puzzle it out for yourself, read no further. You have been warned!

**The answer appears below if you highlight the area with your mouse - I've coloured the text to be the same as the background so it doesn't appear without highlighting**

"A false path. At one point we thought it was tracking the mouse. Haha. Except it isn't. Even if you don't touch the mouse amazingly it always gets the right answer. Hehe.

Half the solution, because there are two tricks at work here, not just one: if you do the math, you'll see that every possible result has to be a multiple of nine. Any two-digit number can be expressed as a*10 + b. (For 73 a=7, b=3). Now the puzzler requests that we subtract the sum of a and b from the number, a*10 + b - (a + b), which becomes a * 9 if you reduce it. Therefore it's a multiple of nine.

The second half of the solution: note that the glyphs of all the multiples of nine are the same.
They are? Yes, they are. That's the trick!
Every time we refresh the screen the symbols change, unbeknownst to us. It gets better. 90 and 99 which are multiples of nine, have different symbols from the other multiples of nine. But there's no way to get those numbers to come out the other end of the algorithm. Nice twist."

Don's Amazing Puzzle
Please read this sentence.





Count the F's.
How many did you find?

**The answer appears below if you highlight the area with your mouse, as above**

There are six F's in the sentence.
There is no catch.

I, like everyone else, found three. I went back and counted and recounted, and I was sure there were just three. So I did a search for 'F' on the page to see what was going on, and sure enough if you do the same on this page (CNTRL-F / APPLE-F in your browser) it will find all six! Mystifying how our brains work.

Both really great tricks.


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