Wikipedia:Reference desk/Archives/Mathematics/2007 July 14

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July 14

combinations

hello,

could someone please help me fill in this table of combinations when you are using the numbers 0 to 9

thanks,

amount of numbers	combinations
1	1
2	90?
3
4
5

Please take a look at our article Combinatorics. We can help you more if you specify what kind of combinations you have in mind. -- Meni Rosenfeld (talk) 12:09, 14 July 2007 (UTC)

Isn't the first row 10 if you consider all single digits as combinations? Or if you are not considering single digits as combinations then shouldn't it be 0? Also does combination like "07" count as a 2 digit combination? (from your data it seems like it doesn't count) If both of the examples above are considered valid combinations then the number of combination is 10ⁿ where n is the amount of numbers, since that's by definition how the decimal system works. --antilived^{T | C | G} 12:15, 14 July 2007 (UTC)

Assuming that 1 is a mistake for 10, another possible explanation of the 90 entry is that all digits have to be different. In that case a formula for the number of combinations/permutations is 10!/(10-n)!, where n is the length of the sequence.  --Lambiam 13:25, 14 July 2007 (UTC)

Additionally we should note that the the number of combination is 10ⁿ where n is the amount of numbers rule given by antilived above works for any positional numeral system, not just for decimal one. One must just take 10 in the appropriate system. --CiaPan 17:10, 14 July 2007 (UTC)

Just a thought, although I am not 100% sure. Perhaps the original poster does not mean "combinations" in the mathematical sense of the word. I get the "feeling", if you will, that he is asking this: how many numbers from 0 to 9; how many numbers from 10 to 99; how many numbers from 1000 to 9999; etc. Perhaps that is the intent of the question? (JosephASpadaro 18:57, 14 July 2007 (UTC))

Just had another thought. Perhaps the question posed to the OP deals with real mathematical "combinations". But the OP has incorrectly interpreted the word combinations as I have explained in my post immediately above this one ...? (JosephASpadaro 19:00, 14 July 2007 (UTC))

I despise guessing games. Actually, I don't, but it is still the OP's responsibility to explain what he meant, not our own to guess it. -- Meni Rosenfeld (talk) 20:03, 14 July 2007 (UTC)

Agreed. I was just trying to make heads or tails of a poorly worded question -- probably more for my own peace of mind. (JosephASpadaro 01:14, 15 July 2007 (UTC))

If you mean how many permutations there are...There is a function in Excel called 'permut' that is structured =permut(number, chosen). I don't have excel on my home PC so can't be sure but I think this function will provide you with what you require. ny156uk 18:11, 15 July 2007 (UTC)

Additional mathematics project work 2007 form 5

Long question about Ang, Bakar and Chandran removed, posted by by 210.186.164.3 (Talk) at 15:02, July 14, 2007

As you can read above under "How to ask a question": Do your own homework. The reference desk won't give you answers for your homework. We may try to help you out if there's a specific part of your homework you don't understand, but make an effort to show that you've tried solving it first. Thank you.  --Lambiam 19:09, 14 July 2007 (UTC)

Date of 2,000,000th article?

Hello. Can a math whiz please formulate and calculate the estimated date of the 2,000,000th article, please? Thank you. --75.18.8.144 22:14, 14 July 2007 (UTC)

We have already had this question. If you care enough about the answer, then look through the archives and you will find it under a similar name to the one you posted it under. Algebra man 22:41, 14 July 2007 (UTC)

P.S. It was quite a recent question so you won't have to go back very far. Algebra man 22:45, 14 July 2007 (UTC)

Here it is — Kieff | Talk 23:25, 14 July 2007 (UTC)