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Maths Help Please!

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  • 02-06-2005 1:33pm
    #1
    the smiley one
    Closed Accounts Posts: 362 ✭✭


    k, I'm desperatley needing some maths help so here it goes...

    6c) iii) 2004

    Eight cards are numbered 1 to 8. The cards numbered 1 and 2 are red, the cards numbered 3 and 4 are blue, the cards numbered 5 and 6 are yellow and the cards numbered 7 and 8 are black
    Four cards are selected at random from the eight cards

    Find the probability that the 4 cards selected are

    iii) all of different colours, two odd-numbered and two even numbered.


    k, so I've done the first two parts using fractions and got them right, and I was wondering if you can do this using fractions as well, cuz all the solutions I've looked at use ncr.........and I don't usually use that way and am not really comfortable with it....

    answers on a postcard...

    :)


Comments

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    #2
    Sarah**
    Registered Users Posts: 531 ✭✭✭Sarah**


    is that honours or pass as im looking through the pass nd cant find that Q!


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    #3
    the smiley one
    Closed Accounts Posts: 362 ✭✭the smiley one


    sorry, it's honours..... it's really doing my head in now!!!

    :)


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    #4
    Creamy Goodness
    Registered Users Posts: 26,579 ✭✭✭✭Creamy Goodness


    the smiley one wrote:
    sorry, it's honours..... it's really doing my head in now!!!

    :)
    isn't there a number they give you under the questions where you can go to a website and get the solution?

    i know there is in pass.


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    #5
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    That's with the Edco papers only.


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    #6
    Sarah**
    Registered Users Posts: 531 ✭✭✭Sarah**


    yeah but she is looking for confirmation that she can use a different method then suggested, well smiley the only thing i can suggest is that u work out ur method and if the answers the same then your sorted, if it works out time and again with other similar sums then your on track!


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    #7
    randomfella
    Closed Accounts Posts: 728 ✭✭✭randomfella


    0-E-O-E-O-E-O-E
    1-2-3-4-5-6-7-8
    red-blue-yellow-black

    (i) 8/8.6/7.4/6.3/5 = 8/35

    (ii) 4/8.3/7.4/6.3/5 x 4!/2!.2! = 18/35

    (iii) 1/8.1/7.1/6.1/5 x 4! x 4!/2!.2! = 3/35


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    #8
    the smiley one
    Closed Accounts Posts: 362 ✭✭the smiley one


    yeah, there is and I've gone to it, but it does it using NCR which I'm not used to.....so just wondering if you can do it using fractions....cuz I don't really get the NCR way....

    :)


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    #9
    the smiley one
    Closed Accounts Posts: 362 ✭✭the smiley one


    randomfella wrote:
    0-E-O-E-O-E-O-E
    1-2-3-4-5-6-7-8
    red-blue-yellow-black

    (i) 8/8.6/7.4/6.3/5 = 8/35

    (ii) 4/8.3/7.4/6.3/5 x 4!/2!.2! = 18/35

    (iii) 1/8.1/7.1/6.1/5 x 4! x 4!/2!.2! = 3/35


    explain! :eek:

    :)


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    #10
    2e
    Closed Accounts Posts: 67 ✭✭2e


    THe Department solutions give 3 possible ways of doing this qs.:
    1. 4C2/8C4 = 6/70= 3/35 [you dont want that one just listed it any way!]
    2. {1,3,6,8}, {1,4,5,8}, {1,4,6,7}, {2,3,5,8}, {2,3,6,7}, {2,4,5,7} prob= 6/70= 3/35 [perfectly acceptable to just list them out as there's only 8 nos.]
    3. 4/8 x 3/7 x 2/6 x 1/5 x 4C2= 3/35 [ still uses an element of ncr but when you think about it it makes the most sense as you're taking four nos. odd or even and chosing 2 at a time]
    Hope it helps....
    Are you doing bothe probability questions??


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    #11
    the smiley one
    Closed Accounts Posts: 362 ✭✭the smiley one


    Need a while to get my head around that...

    I avoid them like the plague - cuz I'm just not sure if they are right or not!!! Probably will end up doing one of them, cuz I'm not a fan of vectors....I'll just do the one with more stats n stuff! Well that's the plan anyway....


    :)


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    #12
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Exactly. I hate probability and vectors bore me.

    I have all the other qustions studied so I should be grand, as I have one question to spare. None to spare in Paper 1 though. Damn them middle 2 questions! :rolleyes:


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    #13
    the smiley one
    Closed Accounts Posts: 362 ✭✭the smiley one


    Question 5 is a total breeze!!! it's lovely all you have to know is induction and logs (don't like binomial so much.... but anyway). I thought I was deffo going to do question 4 but the question last year was fairly hard - it took me about 15 mins to work out how to do part c and I know if I was in an exam I'd be panicing and not thinking straight... I really don't like integration, the diagrams and all that stuff p*iss me off cuz they waste so much time - ARGH!
    But it really just all depends on the paper...

    :)


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    #14
    2e
    Closed Accounts Posts: 67 ✭✭2e


    In my mocks I did the two probabilty in 30 mins cos with them you either get most of the marks.... or not. Spending extra time on them is just a waste. If you can get all parts of the two questions attempted in that time then you can do an extra question to cover you in case you make a mistake (which you PROBABly will, I know I did!) I did pure quality in my maths mocks due to that and thats what I'll be doing in the real thing. Just advice that worked for me, you can take it or leave it....


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