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Before measuring something, you need to know what unit to use. You can do this by estimating its approximate length, mass or volume.

Solving calculations of length, mass and capacity might involve converting between standard units. Understanding what kilo-, centi- and milli- mean will help you decide which number to multiply or divide by.

The perimeter of a shape is the total distance around its edge. To calculate the perimeter of a shape, you just have to add up the lengths of all of its sides.

When converting between metric units of area and volume, the numbers you have to multiply or divide by need to be squared for area and cubed for volume.

Two-dimensional shapes are flat. The perimeter of a 2D shape is the total distance around the outside of the shape. The area of a 2D shape is the space inside the shape. Compound shapes can be split into different shapes to work out total area.

An object’s volume is a measure of its total three-dimensional space and can be found using formulae. Volumes of composite objects can be found by breaking them down into simpler objects and adding the volumes together.