Area for the 11 plus

Area is the number of square units inside. Rectangle: length times width. A triangle is half of a rectangle. Base times height, halved. The height must be the straight-up one, at a right angle to the base, never the slanted edge. A parallelogram is base times that same straight-up height.

Base 12, height 5. 12 times 5 is 60. Half of 60 is 30. Thirty square centimetres. For a compound shape, split into rectangles, find each area and add.

The trap is stopping at 60. That is the area of the rectangle, twice the triangle. A good check: the triangle must fit inside the rectangle.

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
• 6.43D 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