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Math Help - arrangement of items after removing some of the items

  1. #1
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    arrangement of items after removing some of the items

    A bag contains 4 red cubic blocks, 3 yellow cubic blocks, . Five cubic blocks are removed randomly from the bag and arranged in line . How many arrangements are possible?

    the ans is 8 .

    my working is 7P5/(4! X 3!) =17.5 .

    my ans is rather weird.
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  2. #2
    Super Member Matt Westwood's Avatar
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    Re: arrangement of items after removing some of the items

    I make it 25.

    You take 5 blocks out: they can be:
    a) 4 red, 1 yellow
    b) 3 red, 2 yellow
    c) 2 red, 3 yellow.

    There are 5 ways of arranging (a) and 10 ways each of arranging (b) and (c). I will leave it to you to do the work.
    Thanks from delso
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    Re: arrangement of items after removing some of the items

    hi, do you mean the ans provided is wrong?

    i folloow your working , 5!/4! + 5!/(2! x 3!) + 5!/(3! x 2!) = 25
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    Super Member Matt Westwood's Avatar
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    Re: arrangement of items after removing some of the items

    Quote Originally Posted by delso View Post
    hi, do you mean the ans provided is wrong?

    i folloow your working , 5!/4! + 5!/(2! x 3!) + 5!/(3! x 2!) = 25
    Presumably -- unless you stated the question wrong.
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