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My thoughts and experiences in Delft.
It's just life, so don't worry.
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Oh woeful number 7

Posted 05-19-11 at 05:21 PM by diced
It all started with this post

3 digits, gives 10*10*10 = 1000 numbers,
but e.g. 007, is not really a number, so are all numbers upto 099, including 000, so 100 in total
so that leaves 900 3 digit numbers in total.

Then came seven (good movie btw)

7 can be at each one of those three places. for the first one:
generates 1*10*10 options -> 100
then second and third place generate:
9*1*10 (combinations starting with 0 don't count) ->90
9*9*1 (again the zero's) -> 81
so there are 100+90+81 = 271 possible 3 digit numbers with at least one 7 in it.

Wow, that narrowed it down more than I thougt

Why did I mention 624?
Here's what I did wrong:
I did 9*9*9 (numbers without any seven) - 100 (numbers with leading zero's) - 5 ( already mentioned numbers) = 624.

So actually 629 (3 digit numbers without 7, or leading 0's) is the number of dismissed numbers.
And 666 can also be dismissed (it was guessed, but not my number) Other guesses had a 7 in them, so they were dismissed already.
so 630 numbers are to be dismissed, from a total of 900, leaving 270 possible numbers.

I should have practised Combinatorics a bit more.
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Total Comments 2


  1. Old
    diced's Avatar
    Wrong again!!!

    629 numbers without 7 are to be dismissed,
    by now 5 numbers with a 7 have been guessed, and one without (so 666 was dismissed anyway).
    so 629 + 5 are to be dismissed
    leaving 266
    guesses (up to now)
    327 728 777(3x but counts as one) 723 997 and 666
    Posted 05-19-11 at 05:27 PM by diced diced is offline
  2. Old
    Me-oh-my, this really says a lot about you Diced! LOL

    It says you have more free time on your hands than I do.... AND IM JEALOUS!!!

    I would totally be spending time figuring things like that out and sharing it on my blog too if I didn't have kids screaming for attention all the time.

    Numbers are my passion! :D
    Posted 06-10-11 at 06:57 PM by Blueranne Blueranne is offline
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