Partitioning is a method taught in Key Stage 1 for adding and subtracting large numbers by breaking them down into place value components. Numbers are written as a number sentence showing their tens and ones. The tens are added together first, then the ones, making large calculations easier to work out mentally. Partitioning helps children visualize math problems and understand that two-digit numbers are made up of tens and ones. While useful for addition, partitioning can cause errors for subtraction, so number lines are often used instead.