The probabality of selecting a HD is
(20+5)/(25+15) * (24)/(39)
There are longer and more complicated of working this out.
a box contains 25 computer diskettes, 5 of which are double density and the remiander are high density. A second box contains 15 diskettes, 10 double density and 5 high density. A box is selected at random and then two diskettes are chosen randomly from the selected box. What is the probability that both diskettes are high density?
2 answers
can you explain?