
Lana
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So you think you know your math huh...
#1455338  04/13/03 09:10 PM (14 years, 8 months ago) 


I'm out with some friends over the weekend and we get into a discussion about numbers. One of my friends brings up a class she had in high school, trig 101.
Anywho, she's trying to tell me that there are only so many combinations of putting 4 digits. In other words, she tried telling me that if you were to use the numbers 0 thru 9 in a four digit sequence, and the numbers can come up as many times as possbile, you'd only have a few (under 10,000 combinations)???
How wrong is that !!!
I tried telling her that if you have 0  9 and they can come up over and over again, you'd have millions of combinations. For example, 1234 or 2255 or 9999
My point is, I want to prove this girl wrong! If I can she's owes me dinner.
Isn't there a formula that can tell you how many combinations there are in a sequence of numbers based on the number of digits there are? If so let me know cause my mouth is watering for a good steak dinner!
Thanks, Lana
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trendal
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Re: So you think you know your math huh... [Re: Lana]
#1455572  04/14/03 06:54 PM (14 years, 8 months ago) 


Yes the formula is:
b^n
where b is the base system you are using (decimal is 10, binary 2, octal 8, ect) and n is the number of places you have.
So for a four digit number in decimal, you have:
10^4 = 10000
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And every line believed
Curriculum's been set
Logic is a threat
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ToxicMan
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Re: So you think you know your math huh... [Re: Lana]
#1455584  04/14/03 06:59 PM (14 years, 8 months ago) 


Shouldn't the number of combinations be equal to the number of combinations for the first digit times the number for the second times the third times the fourth? Since there are 10 possible values for each digit, the total number of combinations should be 10x10x10x10 = 10,000. It's equivalent in this case to asking how many numbers there are from 0000 to 9999, which is exactly 10,000.
If you're not allowed to have a duplicate digit in the number, then the total is 10x9x8x7 = 5040 possible combinations.
Or the question is something else from either of those.
 Happy mushrooming!

trendal
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Re: So you think you know your math huh... [Re: ToxicMan]
#1455708  04/13/03 11:57 PM (14 years, 8 months ago) 


Shouldn't the number of combinations be equal to the number of combinations for the first digit times the number for the second times the third times the fourth?
That's the same thing as the formula i posted
10x10x10x10 = 10^4
 The story book's been read
And every line believed
Curriculum's been set
Logic is a threat
Reason searched and seized
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Anno
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Re: So you think you know your math huh... [Re: Lana]
#1456112  04/14/03 03:34 AM (14 years, 8 months ago) 


You gave yourself the answer already in your question, the highest combination is 9999 and the lowest 0000 and all the combinations inbetween, so all in all 10,000 combinations

Jackal
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Re: So you think you know your math huh... [Re: Lana]
#1456171  04/14/03 04:11 AM (14 years, 8 months ago) 


I think you're thinking of the number of sequences of 4 numbers between 1 and 1000.
e.g.
1  65  743  998
or
321  555  601  677
In this case the number of possible combinations = (1000*999*998*997)/(1*2*3*4) = (994010994000)/(24) = 41,417,124,750


ExtravagantDream
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Re: So you think you know your math huh... [Re: Jackal]
#1456272  04/14/03 04:59 AM (14 years, 8 months ago) 


the number of sequences of 4 numbers between 1 and 1000 would be just 24. The numbers 998 or 65 is the whole number and cannont be split. So they would have to stay as (998)(65). They cannon be thrown together such as 96958.
It would be the number of 4 digit sequences.. or something like that. I know what you ment to say, but it can be interpreted differently.

Lana
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AH CRAP!!! Its 10,000!
Now I owe my friend dinner! Thats the last time I get into a conversaton at 1:00 a.m. after drinking greyhounds all night!
Thanks guys... I appreciate your help.
Lana
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trendal
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Re: So you think you know your math huh... [Re: Lana]
#1456723  04/14/03 11:48 AM (14 years, 8 months ago) 


lol
 The story book's been read
And every line believed
Curriculum's been set
Logic is a threat
Reason searched and seized
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neuro
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Re: So you think you know your math huh... [Re: Lana]
#1460286  04/15/03 02:36 PM (14 years, 8 months ago) 


You either want to do a nCr or an nPr equation.
nPr =
n!/([nr]!)
where n is the total number of items (in your case 10) and r is how many you're taking at a time but nothing can be repeated
and nCr =
n!/[r!*(nr)!]
where n = 10 and r = 4
Edited by neuro (04/15/03 02:46 PM)

djfrog
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Re: So you think you know your math huh... [Re: neuro]
#1462812  04/16/03 03:27 AM (14 years, 8 months ago) 


23.40?

Anno
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Re: So you think you know your math huh... [Re: neuro]
#1463132  04/16/03 08:43 AM (14 years, 8 months ago) 


nPr = n!/([nr]!) ) = 10! / (104)! = 5040
nCr = n!/[r!*(nr)!] = 10! / [4! (104)!] = 210
So these are your solutions ??! Hmmmmm nope, won?t be right....

matts
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[Re: Anno]
#1463203  04/16/03 10:04 AM (14 years, 8 months ago) 



Anno
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Re: So you think you know your math huh... [Re: matts]
#1463219  04/16/03 10:22 AM (14 years, 8 months ago) 


>because nothing can be repeated:
Says who?

neuro
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Re: So you think you know your math huh... [Re: Anno]
#1463234  04/16/03 10:35 AM (14 years, 8 months ago) 


those are the solutions if nothing can be repeated...
the easier way to figure it out, allow for numbers to be repeated, in the case 0001 three 0's would to assign 1  1 relationships to the combinations 1) 0000 2) 0001 3) 0002 4) 0003 and so on... so whatever the last 4 digit number is the counting number assigned to it will the 4 digit number + 1

matts
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[Re: neuro]
#1463382  04/16/03 12:11 PM (14 years, 8 months ago) 


Edited by matts (04/16/03 12:21 PM)

ExtravagantDream
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Re: So you think you know your math huh... [Re: matts]
#1464167  04/16/03 04:57 PM (14 years, 8 months ago) 


Absolutely correct.. and dont make me write them out to show it.

djfrog
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Re: So you think you know your math huh... [Re: neuro]
#1464802  04/16/03 07:54 PM (14 years, 8 months ago) 


Hah, well, if it were a nail, my hammer would've worked. And I suppose if she were asking for permutations, some fancy factorial moves would have worked.
I still don't think anyone's solution has accounted for 34.68 though. So, still, no ones been right yet.

trendal
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Re: So you think you know your math huh... [Re: djfrog]
#1466090  04/17/03 03:01 AM (14 years, 8 months ago) 


34.68 is the same as 3468 in this case
 The story book's been read
And every line believed
Curriculum's been set
Logic is a threat
Reason searched and seized
BTC  1KqrSHZ1C3NsQP4g3PkHhppBnhdgyXr6sB

JssMthrFcknChrst
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Re: So you think you know your math huh... [Re: trendal]
#1466109  04/17/03 03:14 AM (14 years, 8 months ago) 


Quote:
and dont make me write them out to show it
You shouldn't have said anything.
Count em yourself...
EDIT: Insert 0000  9999 here

Edited by JssMthrFcknChrst (04/24/03 05:43 AM)

