"Mrs. P is your cardboard teacher. She will help you verbalise your mathematical reasoning in order to explain how you worked out your answers. Each card has a sentence written on it, with blanks for the children to fill in. For example: I know … therefore I know …. Using these prompts, children can push their thinking forward and explain how they are attempting to solve a mathematical puzzle. It will enable them to draw on previous knowledge and extrapolate from the number facts known."