In the previous lesson, students used base-ten blocks to represent division and represented their work on paper. This lesson focuses on base-ten diagrams to represent dividing by decomposing the dividend by place value—decomposing a larger unit to 10 of a smaller unit—and by reasoning in terms of equal-size groups. Students recall that they can exchange or decompose one or more units of a higher place value for 10 units of the next lower place value in order to have enough units to put into equal groups. This lesson sets the groundwork for the reasoning students use in a future course when they learn to divide multi-digit numbers using the standard division algorithm, which relies on dividing by place value, one digit at a time.