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P6 Angle chasing

Today’s problem — free all day, every step. Every day has one.

A trellis and a lattice — angle EAB

A landscaper installs a triangular trellis EAD in a garden bed, with a parallelogram lattice panel BCDE fitted inside it; B lies on the trellis edge AD. The posts AB and BE are equal in length. Given angle DBC = 46° and angle BCD = 70°, find angle EAB.

One step of the worked solution to A trellis and a lattice — angle EAB, drawn in pencil.
6 steps, drawn in pencil

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The pattern behind it: Angle chasing

One angle gives you the next, until you reach the angle asked for.

In this one. The parallelogram carries the angle at D across to B, and that angle is the exterior angle of the isosceles triangle — so the angle at A is simply half of it.

62°1u1uthe pair share what is left: 118 ÷ 2 = 59°

How to spot it

A figure has several angles marked with only one or two values given, and words like 'isosceles', 'parallel', or 'straight line' point to which rule to use first.

Common mistake

Children apply an angle rule to the wrong triangle or the wrong straight line in a crowded figure, or stop one step before the angle actually asked for.

Try one like it

Challenging A display easel — angle EAB A framer is building a triangular display easel EAD, braced by a parallelogram strut BCDE, where B lies on strut AD. The two strut…
All 4 with this pattern →

The 33 problem patterns

All 33 patterns, one to a page — the 19 behind Primary 5 and 6 word problems, and the skills the younger years are built on. The bar model, how to spot it in the question, and the mistake children make. A booklet you can print. Free.

A PDF, and a note when new solutions go up.