If Karl can wash 6 cars or wax 3 cars per hour while Tom can wash 3 cars or wax 3 cars per hour .?

Karl has a higher productivity rate than Tom in both washing and waxing cars. Specifically, Karl can wash double the number of cars per hour compared to Tom (6 vs. 3). In terms of waxing, they are equal at 3 cars per hour. Therefore, if efficiency is the goal, Karl is the more effective worker for washing cars, while both are equally effective for waxing.