GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Three tools are taken out of a tool box having ten different machine
[#permalink]
11 Nov 2024, 00:47
11 Nov 2024, 00:47
Expert Reply
00:00
Question Stats:
33% (02:03) correct
66% (03:27) wrong based on 3 sessions
Hide Show timer Statistics
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
- Part of the project: GRE Quant & Verbal ADVANCED Daily Challenge 2024 Edition - Gain 20 Kudos & Get FREE Access to GRE Prep Club TESTS
- Also replying to the unanswered questions
Re: Three tools are taken out of a tool box having ten different machine
[#permalink]
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
[#permalink]
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
