These worksheets are designed to be mental arithmetic activities.

There are many ways in which these questions could be used. Possibly the worksheets could be handed out to students (they are ready to photocopy) but more likely only a selection of questions will be used, perhaps from an overhead transparency. Students could work on selected questions individually and then discuss in groups, explaining their methods and why the methods work.

Please see Teaching computation in the calculator era for some general principles and goals of teaching mental computation.