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Three tools are taken out of a tool box having ten different machine
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11 Nov 2024, 00:47
11 Nov 2024, 00:47
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Question Stats:
53% (01:40) correct
46% (03:58) wrong based on 15 sessions
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Three tools are taken out of a tool box having ten different machine tools. If three out of the 10 tools in the tool box are defective, what is the probability of taking out exactly two defective tools?
A. 1/40
B. 3/20
C. 7/40
D. 7/20
E. 21/40
A. 1/40
B. 3/20
C. 7/40
D. 7/20
E. 21/40
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Re: Three tools are taken out of a tool box having ten different machine
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11 Nov 2024, 12:43
11 Nov 2024, 12:43
Carcass, can you please share a solution to this question?
Re: Three tools are taken out of a tool box having ten different machine
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11 Nov 2024, 15:16
11 Nov 2024, 15:16
Expert Reply
Think practically
You have 3 defective out of ten, so the NON defective are 7
Among the defective you can pick one no good and the other two good in a simple order
D,D,ND
D,ND,D
ND,D,D
3 ways
Now, imagine to pick up a tool among 10 and you have three possibilities 3/10
Now the next so 2/9
Now the next 7/8 because you need to pick three tools and 2 are defective that's why the last one is 7 because the NOn defective
Now the last part 3* (3/10*2/9*7/8)=7/40
C is the answer
You have 3 defective out of ten, so the NON defective are 7
Among the defective you can pick one no good and the other two good in a simple order
D,D,ND
D,ND,D
ND,D,D
3 ways
Now, imagine to pick up a tool among 10 and you have three possibilities 3/10
Now the next so 2/9
Now the next 7/8 because you need to pick three tools and 2 are defective that's why the last one is 7 because the NOn defective
Now the last part 3* (3/10*2/9*7/8)=7/40
C is the answer
