3D shapes for the 11 plus

Three words. A face is a flat surface. An edge is where two faces meet. A vertex is a corner. A cube has 6 faces, 12 edges and 8 vertices. A triangular prism has 5 faces, 9 edges and 6 vertices. A square-based pyramid has 5, 8 and 5. A net is a shape opened out flat.

Count the prism one set at a time, including the back. Two triangle ends, with three edges each: 6. Three edges joining them: 3. Nine in total.

The trap is counting only what is drawn solid, and missing the dashed ones at the back. Another check: faces plus vertices, take away edges, makes 2. For the prism, 5 plus 6 take away 9 is 2.

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
• 6.5Volume and capacityVolume means multiply, never add
• 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