"Rod Speed" wrote in message
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"NY" wrote in message
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"tim..." wrote in message
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"harry" wrote in message
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https://www.youtube.com/watch?v=z7tRr49qZfo

So, how do you account for this well known trick?

you really can't work it out for yourself

Nice one. I think I've worked it out:

No you havent.

I presume lines that are supposed to be parallel aren't.

http://andyburns.uk/misc/chocolate-trick.png

Ah, the difference is that the combined length is shorter. I hadn't spotted
that. I wondered whether the difference was that the diagonal edges of the
two pieces were not quite parallel, and that the area of the extra piece was
the area of a triangular air gap between the pieces. But I was wrong.