70% of all parts come from the first machine, and 30% from the second.

70% of all parts come from the first machine, and 30% from the second. Among the parts of the first machine, 4% are defective, and the second – 5%. Then the probability that the quality part received for the assembly is equal to

1) 4%: 100% = 0.04 (part) of the parts of the first machine are defective.

2) 1 – 0.04 = 0.96 (part) of the parts of the first machine are of high quality.

3) 0.96 * 70% = 67.2 (%) of the total number of parts are of high quality and came from the first machine.

4) 5%: 100% = 0.05 (part) of the parts of the second machine are defective.

5) 1 – 0.05 = 0.95 (part) of the parts of the second machine are of high quality.

6) 0.95 * 30% = 67.2 (%) of the total number of parts are of high quality and came from the second machine.

7) 67.2 + 67.2 = 95.7 (%) of all quality parts.

Probability:

8) 95.7%: 100% = 0.957.