Angle facts for the 11 plus

Four facts to learn. Angles on a straight line add to 180. Angles round a point add to 360. Angles in a triangle add to 180. Angles in a quadrilateral add to 360. Each one is a total, and the missing angle is what is left.

65 plus 48 is 113. 180 take away 113 is 67. A quadrilateral with 90, 110 and 75: add those to 275. 360 take away 275, 85. An isosceles triangle with a top angle of 40: the other two are equal, so 140 split into two, 70 each.

The trap is mixing up the totals. A triangle uses 180. Using 360 for it gives 247, bigger than any triangle angle could be. No angle in a triangle can be more than 180.

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
• 6.5Volume and capacityVolume means multiply, never add
• 6.6Types of angle and measuringGuess first, then read the scale
• 6.8Position and coordinatesAlong the corridor, then up the stairs

Every 11 plus maths topic