Derek discusses the importance of measurements in primary mathematics. He argues that it is in the context of measurements in various kinds that we find ‘realistic and relevant applications of number skills’. He outlines different things that can be measured: length, time, temperature and solid volume. It is stressed that before measuring these things the meaning of these concepts must first be understood. The difference between volume and capacity is given as an example. Derek defines volume as about ‘a three-dimensional space that something takes up’ and holds up a cube with a volume of one thousand cubic centimetres which is the amount of three-dimensional space that it occupies. He then explains that the capacity of a container is the volume of liquid that it can hold.

The next stage of the video starts with Derek stating that whatever measuring concept that children learn about there are always the same key stages to go through. These stages are outlined including being able to compare objects and then ordering more than two items into a sequence depending on capacity. Haylock stresses the importance of ensuring children are measuring using non-standard units before going on to measure standard units. He briefly explains the prefixes used for standard units: deci, centi, milli. The final principle that Derek thinks is key to the subject of measurement in that all measuring is approximate, this is explained in further detail.