A 8 year old boy has 6 different toys and wants to put them all in a straight line. In how many ways can this be done? I w

Question

A 8 year old boy has 6 different toys and wants to put them all in a straight line.
In how many ways can this be done?

I would appreciate step by step, as I have no clue on how to solve. Thanks!

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Gia Bảo 2 months 2021-08-04T10:10:28+00:00 1 Answers 1 views 0

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    2021-08-04T10:12:11+00:00

    Answer:  720

    ============================================================

    Explanation:

    The number 8 from “8 year old boy” can be completely ignored. In my opinion, this is an (un)intentional distraction on your teacher’s part.

    There are 6 toys to arrange. The order is important.

    • For the first slot, there are 6 choices.
    • Then the second slot has 5 choices (we cannot have a toy occupy more than one slot at a time).
    • The third slot has 4 choices, and so on.

    We have this countdown: 6,5,4,3,2,1

    Those values multiply out to 6*5*4*3*2*1 = 720

    There are 720 ways to arrange the 6 different toys. Order matters.

    ———————

    An alternative approach is to use the nPr permutation formula with n = 6 and r = 6. We use a permutation because order matters.

    The nPr formula is

    _{n} P _{r} = \frac{n!}{(n-r)!}\\\\

    where the exclamation marks indicate factorial. For example, 6! = 6*5*4*3*2*1 = 720.

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