Volume and capacity for the 11 plus

Volume is how many unit cubes fit inside. Stack the layers. One layer is length times width. Then the number of layers is the height. So volume is length times width times height. Capacity is how much liquid it holds. One litre is 1,000 cubic centimetres.

5 times 4 is 20, a layer. Three layers: 60 cubic centimetres. A tank 20 by 10 by 15 centimetres holds 3,000 cubic centimetres, which is 3 litres.

The trap is adding the three sides, 12, because adding gives a length, not a volume. The units give it away: cubic units need three multiplications.

Part of the Geometry topics for the 11+.

• 6.1Properties of 2D shapesFold it in your head before you count
• 6.2Perimeter and missing lengthsPerimeter is a walk, not a space
• 6.3AreaUse the height that stands up straight
• 6.43D shapesCount the edges you cannot see
• 6.6Types of angle and measuringGuess first, then read the scale
• 6.7Angle factsKnow the total, find what is left
• 6.8Position and coordinatesAlong the corridor, then up the stairs

Every 11 plus maths topic