Properties of 2D shapes for the 11 plus

Shapes are sorted by their sides and angles. Triangles: equilateral has three equal sides, isosceles has two, scalene has none. Quadrilaterals have four sides. A square has four equal sides and four right angles. A rectangle has opposite sides equal and four right angles. A rhombus has four equal sides but no right angles needed. A parallelogram has two pairs of parallel sides. A circle has a radius from the centre to the edge, and a diameter, which is twice the radius.

A line of symmetry is a fold that makes two halves match exactly. Fold a rectangle down the middle each way: that is two lines. The diagonals do not work. The corners do not match up.

The trap is counting diagonals, because a square does have them. A rectangle that is not a square does not. Fold it if you can, in your head, and check the halves land on each other.

Part of the Geometry topics for the 11+.

• 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
• 6.5Volume 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