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
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.