You and your friend each collect rocks and fossils. Your friend collects three times as many rocks and half as many fossils as you. You collect 20 objects. Your friend collects 15 objects. How many rocks and how many fossils do you each collect?

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297