3734. The assembly shop received parts from three machines. The first machine made 51% of the parts of their total number, the second machine 24% and the third 25%. In this case, the first machine tool produced 90% of the first-class parts, 80% in the second and 70% in the third. Using the formula of the total probability to determine what is the probability that the item taken at random will be of the first grade?

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)