Answer:
Step-by-step explanation:
If a watch has fewer than three defects, then either 1.) It has no defects, 2.) it has exactly 1 defect, or 3.) it has exactly 2 defects.
1.) The probability that the watch has no defects is , because for every chime there is a probability of
that there is no defect
2.) The probability that the watch has exactly 1 defect is times the number of ways you can choose 1 of 75 of the chimes to be defective, which is
, so the probability that the watch has exactly 1 defect is
.
3.) For the same reason as 2.), the probability that the watch has exactly two defects is
Since 1.), 2.), and 3.) are mutually exclusive events, the probability of their union is simply the probability of each of them added together, which is