Probability on Defective Tyres

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rahulranjan86

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Feb 18, 2012
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If 3 of 20 tyres are defective and 4 of them are randonly chosen for inspection, what is the probablity that only one of the defective tyres are included?

My Attempt:

= (3C1 * 17C3) / 20C4

= 0.4211

Book Answer: 0.889

Not sure where I am going wrong. :?:
 
If the problem is "the probablity that only one of the defective tyres are included" then the book is wrong. I haven't done the calculations but I suspect that the book is giving the probability that "at least one tyre is defective".
 
Either the book is wrong or the question is NOT "the probablity that only one of the defective tyres are included".
 
rahulranjan86 said:
If 3 of 20 tyres are defective and 4 of them are randonly chosen for inspection, what is the probablity that only one of the defective tyres are included?
My Attempt:
= (3C1 * 17C3) / 20C4
= 0.4211 Book Answer: 0.889
Click to expand...
As the question is written, your answer is correct.
 
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