Name it, then write the total down: angles
The Short Answer
Four totals cover almost every missing-angle question: a straight line is 180 degrees, angles round a point make 360, a triangle makes 180 and a quadrilateral 360. Name the angle before calculating — acute, right, obtuse or reflex — then write the total down, subtract what you are given, and check the answer suits the picture.
What is an angle question?
Nearly always a missing angle. Your child is shown a diagram with some angles marked and one unknown, and asked to find it.
By Year 5 they can already tell acute from obtuse. What earns the marks is knowing which total they are working with, and checking the answer against the picture in front of them.
The four totals
These four are the whole topic, more or less.
| Situation | Total |
|---|---|
| Angles on a straight line | 180° |
| Angles round a point | 360° |
| The three angles of a triangle | 180° |
| The four angles of a quadrilateral | 360° |
Almost every missing-angle question is one of those with something taken away from it.
Name it first
Before looking at the numbers, name the angle you are trying to find: acute, right, obtuse or reflex.
That gives a range the answer must fall in — acute is under 90, obtuse is between 90 and 180, reflex is over 180 — and the range catches errors the arithmetic will not.
Where do pupils lose marks?
Using the wrong total — 180 for a shape that needed 360, most often.
Skipping the naming check, and writing an obtuse answer for an obviously acute angle.
Measuring a diagram that says it is not drawn to scale.
Missing an angle in a round-a-point question, so the subtraction is short by one.
Try it yourself
Name the angle you are looking for first, then write down which total applies.
- Two angles sit on a straight line. One is 115°. What is the other?
- Three angles meet at a point. Two are 90° and 145°. What is the third?
- A triangle has angles of 63° and 49°. What is the third?
- A quadrilateral has angles of 100°, 85° and 90°. What is the fourth?
- Before calculating question 1, what kind of angle should the answer be?
- 65°. Straight line, so the total is 180, and 180 − 115 = 65.
- 125°. Round a point, so the total is 360, and 360 − 90 − 145 = 125.
- 68°. Triangle, so the total is 180, and 180 − 63 − 49 = 68.
- 85°. Quadrilateral, so the total is 360, and 360 − 100 − 85 − 90 = 85.
- Acute. The other angle is 115°, which is obtuse, so what is left of 180 must be less than 90. Naming it first means an answer of 165° would have been rejected before it was written down.
How much practice does this type need at home?
Two minutes at a time, and mostly on the naming rather than the arithmetic.
Point at angles around the house — the corner of a door left ajar, the hands of a clock, a slice cut from a pizza — and ask: acute, right, obtuse or reflex? Then ask roughly how many degrees.
A child who can estimate an angle by eye has a permanent check on every answer they produce, and it costs nothing to build.
Free: a Maths workbook
Questions across the Maths question types, with the method printed at the top and full answers at the back. One workbook for the whole strand, not a sheet per question type.
Frequently Asked Questions
Why name the angle before calculating?
Because it gives you a range the answer has to fall in, and that range catches most errors instantly. If the angle in the diagram is clearly acute, the answer must be under 90 degrees — so an answer of 165 is wrong and you know it without rechecking the arithmetic. Naming takes about two seconds and it is the cheapest error check in the topic.
Which four totals matter?
Straight line 180. Round a point 360. Triangle 180. Quadrilateral 360. Almost every missing-angle question you will meet is one of those with one or more angles removed. Learn them as four facts and the topic becomes a subtraction, which is what it mostly is.
What if the diagram is not drawn to scale?
Papers usually say so, and where they do, the picture cannot be measured — but it can still be judged. An angle drawn as clearly obtuse will not turn out to be 40 degrees even in a rough diagram, so the naming check still works. What you must not do is get out a protractor and read an answer off a diagram that says not to.
How should my child set the working out?
Write the total first, on its own line, before touching the given numbers. 'Straight line = 180.' Then subtract. Children who begin by writing the numbers they were given often subtract from the wrong total, and the working shows nothing that would reveal it. Starting with the total makes the mistake visible.
Sources
- GL Assessment — 11+ familiarisation materials and question type descriptions Published 2025.
- Clever Clogs Academy — our own Year 4 and Year 5 lesson records, Winslow Published September 2025 to July 2026.
We are not affiliated with, endorsed by or connected to GL Assessment or Buckinghamshire Council. Test arrangements change; always check the council's own pages for the current year's dates.
We Teach This Method Every Week in Winslow
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