11 July 2009

A puzzle

229, expressed in base 10, is a nine-digit number. All nine of its digits are different. Find the digit that is missing without explicitly calculating 229. (Thanks to Kate for this one; a solution is there, so don't look until you've thought about it.)
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7 comments:

Anonymous said...

I like it!

July 11, 2009 at 5:38 PM
Vishal said...

Oh, this is so uninteresting! The puzzle is too amenable to a calculator-based solution.

July 11, 2009 at 10:23 PM
CarlBrannen said...

Got it. Very nice.

July 11, 2009 at 10:24 PM
Anonymous said...

Got it (I think) and I'd have to suggest to Vishal at number 2 that the non-calculator trick is quite cute.

Yemon

July 12, 2009 at 5:12 AM
Pete said...

Cool. I got it. It's one of those problems that's a lot easier if you trust Kate and assume a solution exists.

July 12, 2009 at 11:17 AM
Qiaochu Yuan said...

Problems like this crop up at local math competitions from time to time (at least they did in my area). It's the kind of problem that ensnares people too used to their calculators, which is why I like it.

July 14, 2009 at 10:41 AM
Anonymous said...

I read the solution at Kate's page.
The solution is not easy and not fast at all. It's a problem to solve with a calculator, too many time spent.

July 14, 2009 at 3:32 PM

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