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# 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

- cidyahLv 77 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

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