CONDITIONAL PROBABILITY -- INTERPRETING THE WORDS "GIVEN THAT"

Find the indicated probability. Express your answer as a simplified fraction unless otherwise noted.

4) The table below shows the soft drinks preferences of people in three age groups. cola root beer lemon-lime

under 21 years of age between 21 and 40 over 40 years of age

40 25 20 35 20 30 20 30 35

If one of the 255 subjects is randomly selected, find the probability that the person drinks root beer given that they are over 40.