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Mental Arithmetic (Posted on 2003-10-05) Difficulty: 3 of 5
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?

See The Solution Submitted by nellie    
Rating: 3.3333 (6 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Some Thoughts another path? | Comment 6 of 20 |
Wouldn't the fact that 1667 is close to 10,000/6 make for an easier method? I haven't worked out the details, but it might be more straightforward than the division by 3 method, at least for the first few digits.
  Posted by Charlie on 2003-10-05 14:36:43
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