For many quantitative subjects, you may want to plan out a sequence of short questions aimed at helping students work their way through a problem, or grasp a better understanding of a theory or model. A number of class teachers in Economics, Maths, Statistics and Accounting and Finance use this approach. Some will go round the class more or less sequentially, so students know when their "time" to answer is approaching and can prepare. Others take a more random approach, calling on people by name. Yet others ask questions to the group as a whole, and let whoever wishes to respond.