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Drew
Lv 5
Drew asked in Science & MathematicsMathematics · 10 years ago

How many possible sets of 25 can I get from 200?

If I had 200 numbered balls (each one unique), and I wanted to create 8 sets of 25, how many different combinations are possible? I can only use each ball once per run, and need to use all each time. I can only have 25 balls in each set, and need to have 8 sets. However, I want to discount any sets that are the same, just in a different order from run to run.

In other, hopefully more understandable words, I want to know how many unique options I'd have to create 8 sets of 25 balls from 200 balls. Sorry if this is hard to understand, I've muddled myself up with all my attempts to work this out. I know I should be able to do this, but I keep getting an answer then thinking I'm using the wrong formulas.

Thanks in advance.

4 Answers

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  • M3
    Lv 7
    10 years ago
    Favorite Answer

    first let's solve a mini-problem.

    how many ways can you divide ABCD into 2 distinct parts ?

    let us start with 4c2*2c2 = 4!/(2!)^2 = 6, the way the first answerer has done.

    unfortunately, this is NOT correct because it contains permutations of the 2 parts, eg

    AB|CD & CD|AB will be counted separately.

    to correct for this, we need to further divide by 2! to get 3 as the ans

    the 3 unique partitions are AB|CD, AC|BD & AD|BC

    so on the larger scale of 200 to be partitioned into 8 groups, the formula will be

    200c25*175c25*150c25* ........ *25c25 / 8!

    = 200!/((25!)^8*8!)

    ≈ 5.837 *10^168

    -----------------------

  • 10 years ago

    i know this problem seems hard but you just have to simply it. you need 4 groups because 100/25 = 4. how many ways can you arrange these groups. remember that number!!! now within each group you need to arrangehave 25 balls of that you can only choose 8.. this equation can help N! / ( (N - h)! * h! ).............the ! point means factorial. factorial means that the number is really the product of all its intergers before it up to one example 4! = 4*3*2*1 = 24 3! = 3*2*1 = 6.......in the equation N stands for the number of posible choices for your problem it is 25. h stands for the spots available for you its 8. plug in the number and you should get how many ways those balls can be arranged within the group.........Lastly multiply the number i told you to remember times the number that you calculated and that should give you your final answer

  • ?
    Lv 4
    4 years ago

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  • 10 years ago

    C(200,25) * C(175,25) * C(150,25) * C(125,25) * C(100,25) * C(75,25) * C(50,25) * C(25,25)

    = 200! / ((25!)^8)

    =~ 2.35 * 10^173

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