My Math Forum Unique numbers that can be generated with 3 digits: 2 Qns

 September 28th, 2009, 07:56 AM #1 Newbie   Joined: Sep 2009 Posts: 2 Thanks: 0 Unique numbers that can be generated with 3 digits: 2 Qns How many possible unique numbers can be generated using 3 digits? I would like to know how find this? Which section of mathematics does this question pertain to : Permutations or Combinations ? (Is there such a thing called Combinations in mathematics?)
September 28th, 2009, 08:18 AM   #2
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Re: Unique numbers that can be generated with 3 digits: 2 Qns

Quote:
 Originally Posted by kiechle How many possible unique numbers can be generated using 3 digits? I would like to know how find this?
# of choices for the first digit * # of choices for the second digit * # of choices for the third digit

You can get different answers depending on how you interpret the problem. For example, is 012 valid? What about 111?

Quote:
 Originally Posted by kiechle Which section of mathematics does this question pertain to : Permutations or Combinations ? (Is there such a thing called Combinations in mathematics?)
Elementary probability. Harder versions of the same problem would fall into Combinatorics.

 September 28th, 2009, 09:57 AM #3 Newbie   Joined: Sep 2009 Posts: 2 Thanks: 0 Re: Unique numbers that can be generated with 3 digits: 2 Qns Yes. Both 012 and 111 are valid. So, how many possible unique numbers can be generated using 3 digits?
September 28th, 2009, 11:45 AM   #4
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Re: Unique numbers that can be generated with 3 digits: 2 Qns

Quote:
 Originally Posted by kiechle Yes. Both 012 and 111 are valid. So, how many possible unique numbers can be generated using 3 digits?
How many choices do you have for the first digit? If you can use only 3 and 5 for the first digit and only 7 for the second two, you have 2 * 1 * 1 unique numbers.

 September 28th, 2009, 09:44 PM #5 Newbie   Joined: Sep 2009 Posts: 2 Thanks: 0 Re: Unique numbers that can be generated with 3 digits: 2 Qns 10*10*10 = 1000 it would also include: 000 as one of the 3-digit numbers.
 September 29th, 2009, 07:12 AM #6 Global Moderator     Joined: Nov 2006 From: UTC -5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms Re: Unique numbers that can be generated with 3 digits: 2 Qns Yes. If you want to include numbers like 000, 1000 is the correct answer.

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