Flexible knowledge, knowing multiple approaches for solving problems, is a hallmark of expertise in mathematics. Frequently, the author writes, students memorize only one method of solving a certain kind of problem, without understanding what they are doing, why a given strategy works, and whether there are alternative solution methods. Comparison…

The purpose of "Focus" is to provide coverage of poverty-related research, events, and issues, and to acquaint a large audience with the work of the Institute for Research on Poverty by means of short essays on selected pieces of research. This issue contains the following articles: (1) Changing poverty and changing antipoverty policies…