Mental computation is the process of drawing on known
strategies to solve an arithmetical problem. For example, to find 7 + 8 + 3, a
strategic approach would be to change the order of the addition to 7 + 3 + 8
because you know that 7 + 3 makes 10, a rainbow fact, and that adding 8 to 10 is
easy because 10 is a friendly number.
This book suggests activities that support mental
computation by exploring the Natural
Maths Strategies posters that can be printed from the accompanying CD. The
posters present the early addition and subtraction strategies and lay the
foundation for the understanding and later recalling of addition and
subtraction facts. Knowledge of these strategies ensures that, in a situation
where memory fails or the numbers are too large, the individual has the
confidence to use mental computation to derive the answer.