1It takes four boxes to make 400, so one of those four boxes will have a defective paper clip. In other words, the chance that any one box has a defective paper clip is 1 in 4, or 0.25. Looked at the other way, that a box will have NO defective paper clip, the chances are 3 in 4, or 0.75.
So the answer to (a) is 0.75.
On average, while making 800 paper clips, the machine will make two defective ones, filling eight boxes. The chance that those two defective paper clips will be in the same box is 1 in 8, or 0.125.
Plus, there is still the chance that a box will contain one defective paper clip. So the chance that a box contains one OR two defective paper clips is 0.25 + 0.125 = 0.375, or 3 in 8
So the answer to (b) is 0.375.
