math
posted by anonymous .
If 90% of the households in a certain region have an answering machines and 50% have both answering machines and call waiting, what is the probability that a household chosen at random and found to have an answering machine also has call waiting?
This is what I think...(Am I correct?)
P(answering and call waiting/answering machine)=(.50/.90)=.56 or 56%

DIdn't the probem state that 50 percent have both? Am I missing something here?
I don't read a conditional probabality on the fifty percent. 
have an "answering machine" also has call waiting?

OK,assumeing the problem statement is conditional, then you are correct. 56 percent of those who have answering machine have call waiting also.