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Maths people please help!

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  • 22-03-2009 4:47pm
    #1
    Delta Kilo
    Registered Users Posts: 1,212 ✭✭✭


    I cant understand an A part to a probability question and it is really wrecking my head at this stage. I find probability and statistics fairly easy and can do all parts of most questions but this one is really getting to me!

    Its 2006 Q7. part (a)
    The password for a mobile phone consists of five digits.
    How many passwords are possible?
    The correct solution is 10*10*10*10*10 = 100,000.
    Why is it 10? 10 is 5c2 but why can each digit be chosen twice?


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    #2
    Thomas_S_Hunterson
    Closed Accounts Posts: 6,151 ✭✭✭Thomas_S_Hunterson


    In the decimal system, each digit in the password can be one of 10 possible 'symbols' i.e. 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

    There are 5 digits in th password ergo 10*10*10*10*10


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    #3
    QueenOfLeon
    Closed Accounts Posts: 5,109 ✭✭✭QueenOfLeon


    Delta Kilo wrote: »
    I cant understand an A part to a probability question and it is really wrecking my head at this stage. I find probability and statistics fairly easy and can do all parts of most questions but this one is really getting to me!

    Its 2006 Q7. part (a)
    The password for a mobile phone consists of five digits.
    How many passwords are possible?
    The correct solution is 10*10*10*10*10 = 100,000.
    Why is it 10? 10 is 5c2 but why can each digit be chosen twice?

    There are 10 digits on a mobile phone - 0-9. Each time you pick a digit for a password, you have 10 possible choices...therefore 10*10*10*10*10

    hope that explains it ok :)


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    #4
    thebigcheese22
    Registered Users Posts: 1,379 ✭✭✭thebigcheese22


    Delta Kilo wrote: »
    I cant understand an A part to a probability question and it is really wrecking my head at this stage. I find probability and statistics fairly easy and can do all parts of most questions but this one is really getting to me!

    Its 2006 Q7. part (a)
    The password for a mobile phone consists of five digits.
    How many passwords are possible?
    The correct solution is 10*10*10*10*10 = 100,000.
    Why is it 10? 10 is 5c2 but why can each digit be chosen twice?

    I think the fact its 5 c 2 i just a coincidence... Its 10 to the power of 5 because you can pick 10 numbers each time, theres not a restriction on any of the numbers or its order...
    Hope that helps, haven't done probability since last year! :o


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    #5
    QueenOfLeon
    Closed Accounts Posts: 5,109 ✭✭✭QueenOfLeon


    dammit sean you got in there before me :p


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    #6
    Delta Kilo
    Registered Users Posts: 1,212 ✭✭✭Delta Kilo


    Anne-Marie!! wrote: »
    There are 10 digits on a mobile phone - 0-9.

    I'm an idiot. Sorry. I get it now. Jesus i thought i could think better than that but all that is in my head now is the german bildegeschichtes and irish!

    Thanks everyone for your replies!


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