Re: Three tools are taken out of a tool box having ten different machine
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11 Nov 2024, 15:16
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