By referring to the common errors in subtraction and multiplication activities on this resource, you can see how our 'example' children would have completed these tests and the resulting patterns of their right and wrong answers.

Although a child may have developed their own defective algorithm(s), they may not always be consistent in their application of it. In some cases this may be because they learn as the test prompts them to think more carefully about the task. It also may be because different test items prompt a confused mix of ideas.

After using the tests, compare your results with the completed example tests to look for a similar pattern. Then refer to the possible teaching strategies suggested for some common errors in written subtraction and multiplication.