I can multiply any three-digit number by 1667 in my head, usually in less than 10 seconds.

Also, to make it even more impressive, I come up with the digits of the result in proper order (not in reverse!)

How can I do this?

(In reply to re: solution by mohan)

If I, as the author, can chip in.

Yes I did mean any 3 digit number between 100 and 1000, not just 111 or 222 etc.

I also mean that I declare my answer starting with the most significant digit, ie the left hand digit first.

I am enjoying your various approaches, since although I know how to do it, I have never known why my method works.

Keep going.

Posted by nellie on 2003-10-12 11:26:22