1. A box contains ten fuses of which 3 are defective. Two fuses are selected at random from the box without replacement. What is the probability that exactly one of the fuses selected is defective?
2. A box contains one hundred fuses of which 30 are defective. Ten fuses are selected at random from the box with replacement. What is the probability that no more than 4 of the fuses selected are defective?
Since this is a selection without replacement the probabilities of selecting a defective fuse change from the first selection to the second selection (the population from which to choose changes from 10 to 9 for the second selection and the number of defective fuses remaining depends on whether a good or bad fuse was picked the first time).
There are two ways of selecting exactly one defective fuse: [pick one ...
This solution looks at probability problems: drawing defective fuses out of a box.