posted by puzzled on .
Of all the videotapes in a large shipment, 21% have a defective tape, 16% have a defective case, and 11% have both defects. If you purchase one of the videotapes in this shipment, find the probability that it has the following.
(a) A defective tape or a defective case.
p = .26
(b) A good tape or a good case.
p = ?
(c) A good tape and a good case.
p = .74
Out of 100
10 have only broken tape
5 have only broken case
11 have both broken
26 have something broken
74 are whole
100 - 11 = 89 have a good case or a good tape (or both)