Key Maths is a series of graded activity books that reinforce children's mastery of important skills and concepts as required by the Primary National Strategy for maths at Key Stage 1. Areas covered include algebra, measures, money, fractions and data handling. Key Maths Book 3 includes: numbers to 20, tens and units, addition and subtraction with one number hidden, standard units of measurement (metre/kilogram), days of the week, 3-D shapes and finding the area of 2-D shapes.