In this lecture, students deepen their understanding of metric unit conversions by learning about conversion factors, how to add and subtract measurements with different units, and how to correctly label answers. They practice converting between kilometres, meters, centimetres, and millimetres, and work with mixed-unit problems. Students also learn that moving from a bigger unit to a smaller unit means multiplying by the conversion factor, while moving from a smaller unit to a bigger unit means dividing. Special attention is given to carrying over and borrowing in addition and subtraction of compound units (e.g., m & cm, cm & mm).