MathBrush
←  All problems

P5–P6 Angle chasing

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

Triangle PQR — angle Q is twice angle R

In triangle PQR, angle P = 48 degrees and angle Q is twice angle R. Find the size of angle R.

▶  Watch it drawn
Show the answerHide the answer

angle R = 44° (and angle Q = 88°).

One step of the worked solution to Triangle PQR — angle Q is twice angle R, drawn in pencil.
6 steps, drawn in pencil

The pattern behind it: Angle chasing

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

In this one. The angle sum turns the two unknowns into one known total (132°), and the words "twice as big" split that total into 3 equal units — 2 for Q, 1 for R.

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

Standard Angles on a line — two equal ones and 62° Two equal angles sit on a straight line together with a third angle of 62 degrees. Find the size of each equal angle.
More about Angle chasing →

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.