Angles in shapes, and the area of triangles and parallelograms

Angle facts worth knowing by heart

Angles on a straight line add to $180^\circ$; angles round a point add to $360^\circ$; the angles of any triangle add to $180^\circ$; the angles of any quadrilateral add to $360^\circ$. Nearly every angle question at Stage 6 is one of these four facts plus one subtraction.

Area of a triangle

Area $=\tfrac12\times$ base $\times$ perpendicular height. The height must be at right angles to the base — it is often not the slanted side, and the slanted side is exactly what the question puts there to tempt you.

Area of a parallelogram

Area $=$ base $\times$ perpendicular height. Slide the triangle from one end to the other and a parallelogram becomes a rectangle — that is where the formula comes from, and remembering the picture beats remembering the words.