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Data management

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1) consider the number of grid paths from the orgin in a coordinate graph to each of the following points:

a) (4,7) b) (3,7) c) (4,6)

2) simplify: (n-r)! / (n-r+1)!

3) solve (n+2)!/ (n-1)! = 210

  • Data management - ,

    A),B),C)
    It's like finding the number of ways to arrange 4 1's and 7-0's.
    The number of ways is given by (m+n)!/(m!n!)
    Experiment first with a grid of 2x2, and then a 2x3.

    2.
    (n-r)!/(n-r+1)!
    =(1.2.3...n-r)/(1.2.3...(n-r).(n-r+1))
    =1/(n-r+1)

    3.
    similarly,
    (n+2)!/(n-1)! = 210
    (1.2.3...(n+2))/(1.2.3...(n-1)) = 210
    n.(n+1).(n+2) = 210
    Start with cube root of 210 = 5.9...
    so try 5.6.7=210 OK.
    So n=5,n+1=6,n+2=7

  • Data management - ,

    thank even though im not sure if u woule see this

  • Data management - ,

    You're welcome!

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