# The master, having 10 parts, of which 3 are non-standard, checks the parts one by one until he comes across a standard one

August 3, 2020 | Education

| **The master, having 10 parts, of which 3 are non-standard, checks the parts one by one until he comes across a standard one. What is the likelihood that he will check exactly two details?**

Obviously, the probability of the A1 event is = 3/10, in addition, P = 7/9, since before taking the second part, the master had 9 parts left, of which only 2 are non-standard and 7 are standard. By the multiplication theorem

P = 3/10 * 7/9 = 7/30

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