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nn x nnn = nnnn
Years ago, somehow, I stumbled across a problem. Using only the digits 1-9 (not zero, and no duplications) how many combinations of nn x nnn = nnnn. You can see that it is a 2 digit number multiplied by a three digit number = a four digit number, using only the 9 digits. I have no idea what this problem was called (I presume it has a name...?) and I can`t find a reference to it. Have you heard of this one? I ended up writing a computer program to generate all the combinations and tell me the answer. Yes it`s a cheat, but there are a lot of possible combinations... Not many valid answers, though. Peter
Re: nn x nnn = nnnn
In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.