how to solve this example ?

A shipment of 9 printers contains 3 that are defective .Find the probability that a sample of size 3,drawn from the 9 , will not contain a defective printer.

the probability is .........

3 Answers

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  • 7 years ago

    So first find the total number of possiblities

    you have 9 printers

    that are coming in groups of 3

    so do 9C3

    9*8*7/3*2*1 = 84 total possibilities

    success is if the three printers are chosen from the 6 printers that are not defective

    so do 6C3

    6*5*4/3*2*1 = 20

    So you get 20/84

    5/21 = 23.8% roughly

    hope I helped

  • cidyah
    Lv 7
    7 years ago

    3 printers out of 9 may be chosen in 9C3 = 9x8x7/3x2x1 = 84 ways.

    P( no defective in the sample of 3 ) = (3C0)(6C3) / 9C3 = (1) (20) / 84

    = 20/84

    = 5/21

  • 7 years ago

    p(no defects in 3) =

    (6C3 * 3C0)/(9C3) =

    (20 * 1)/84 =

    20/84 = 5/21

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