use metric units of length (millimetres, centimetres, metres, kilometres), their abbreviations (mm, cm, m, km), conversions between them, and appropriate levels of accuracy and choice of units
3.1.2.3
use formulas to calculate perimeters of familiar shapes, including triangles, squares, rectangles, polygons, circles and arc lengths
3.1.2.4
use formulas to calculate perimeters of familiar composite shapes [complex]
