A class of 30 students was surveyed to see if they knew how to swim or ride a bike. The results are in the Venn diagram shown. venn
What is the probability that a student knows how to swim and ride a bike, given that they know how to swim? [Hint: Look at the number of people who know how to swim - that's the sample space. Of all the students who know how to swim, how many of those can swim and ride a bike?]