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Probability on Defective Tyres

rahulranjan86

New member
Joined
Feb 18, 2012
Messages
9
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. :?:
 

HallsofIvy

Elite Member
Joined
Jan 27, 2012
Messages
4,719
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".
 

HallsofIvy

Elite Member
Joined
Jan 27, 2012
Messages
4,719
Either the book is wrong or the question is NOT "the probablity that only one of the defective tyres are included".
 

pka

Elite Member
Joined
Jan 29, 2005
Messages
7,686
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
As the question is written, your answer is correct.
 

rahulranjan86

New member
Joined
Feb 18, 2012
Messages
9
Thank You!

:p
 
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