Designed and developed by a mathematic curriculum researcher at the Freudenthal Institute at Utrecht University, the rekenrek is an exciting and innovative classroom tool that enhances and supports the natural development of number sense in children. It encourages learning across a range of mathematical skills and concepts, from simple addition and subitization to commutativity, distributive property and fractions. However, despite the potential and versatility of this manipulative, there has been surprisingly little written about either its application or its benefits - until now.When the stacks of rekenreks first arrived at Amy How's school, she was tasked with discovering and explaining their function to the rest of the staff - despite the scarcity of current research or other information. Over the six years since, she has developed her own set of tasks and strategies, which she regularly presents to teachers around the world. These techniques - effective, straightforward and very popular - are the basis of this book.Rekenrek 101 is written in a format that makes for a useful teacher resource: not too long; clear, concise and inspiring enough for readers to try the new ideas the next day in class. It is easy to follow and easy to navigate while demonstrating a simple change in practice that stays up with current trends. This is not a book on theory, but it is based on what the latest research is telling us.