GM5-1: Select and use appropriate metric units for length, area, volume and capacity, weight (mass), temperature, angle, and time, with awareness that measurements are approximate.
This means that when given a measuring task students will identify and use an appropriate metric unit. This involves the choice of an attribute (for example length, area, temperature) appropriate to the problem, the selection of an appropriate measurement tool, and the choice of unit adequate for the task, for example millimetres are needed to measure the length of solid material for construction. Measuring tasks should include a range of attributes and unit sizes, for example measuring the volume of the classroom in cubic metres, measuring the area of a piece of paper in square centimetres.
Students will be aware that measurements are not exact. The accuracy of a measurement can be affected by both human error and the accuracy of units, for example two people may give slightly different values for the width of a crayfish tail. This connects to the concept of rounding to a desired accuracy. Students need to understand that any measure involves a number (quantity) and unit of measure. Both determine the size of the measure, for example 1.80 metres represents a measure that is greater or equal to 179.5 cm and less than 180.5 cm.