Understanding that angles in a triangle always add up to 180° and using this to find missing angles.
Where your child meets this in real life: Calculating angles in roof trusses, triangular structures, or navigation
Each SEAG paper has 28 maths questions. Questions 29 to 50 are multiple choice with five possible answers, and questions 51 to 56 need a short written answer. With 56 questions in 60 minutes across English and maths, that is about a minute per question.
SEAGReady breaks angles in triangles into 3 steps, taught in order so each skill builds on the last.
Find the missing third angle when two angles of a triangle are given
Find angles in isosceles and equilateral triangles using equal-angle properties
Solve multi-step problems using only internal triangle-angle properties
Try three free questions from our angles in triangles course. They start easy and get harder, so you can see where your child's confidence runs out. If they manage the last one without a hint, this topic is probably secure. If not, the steps above show where to start.
The triangle shown has angles of 60° and 65°. What is the third angle?
The isosceles triangle shown has base angles of 55°. What is the apex angle?
In triangle ABC, angle A is 58 degrees and angle B is 40 degrees. What is angle C?
This is the exact interactive worked example your child sees in SEAGReady. Step through it and watch the method build up.
Jack is designing a triangular flag for his school's sports day. Two of the angles measure 55 degrees and 70 degrees.
What is the third angle of the flag?
55° + 70° + ? = 180°
The two given angles are 55° and 70°
Step 1 of 4
Jack is designing a triangular flag for his school's sports day. Two of the angles measure 55 degrees and 70 degrees.
What is the third angle of the flag?
The third angle of the flag is 55°.
The key insight: Every triangle's angles add to exactly 180 degrees - no matter what shape it is!
Common mix-up: Using 360° instead of 180°. 360° is for angles around a point. Triangles always use 180°.
These are the misconceptions we see most often in angles in triangles, including the ones our practice questions are specifically designed to catch.
Struggling with angles in triangles? The real gap is often in one of these earlier topics.
Sitting the SEAG test this November? Read our last-month revision plan, Paper 1 vs Paper 2 and test day guide.
SEAGReady finds the exact step where your child gets stuck, teaches it with worked examples like the one above, and brings it back for review so it sticks.
Free to start · no card needed