Classifying triangles by sides (equilateral, isosceles, scalene) and by angles (right-angled, acute, obtuse).
Where your child meets this in real life: Identifying triangle types in structures, art, and design
SEAGReady breaks classify triangles into 3 steps, taught in order so each skill builds on the last.
Classify triangles as equilateral, isosceles, or scalene based on the number of equal sides
Classify triangles as right-angled, acute, or obtuse based on their largest angle
Describe triangles using both side and angle classifications together (e.g., 'right-angled isosceles')
Three free sample questions from our classify triangles course. Every question comes with a full explanation, and hints that guide without giving the answer away.
The triangle shown has side lengths 9 cm, 9 cm and 13 cm. What type is it when classified by side lengths?
The triangle shown has angles of 40°, 50° and 90°. What type of triangle is it by angles?
The triangle shown has sides 6 cm, 8 cm and 10 cm, and angles 37°, 53° and 90°. Give its full classification.
This is the exact interactive worked example your child sees in SEAGReady. Step through it and watch the method build up.
Lucy is sorting triangular tiles for an art project. One tile has sides measuring 5 cm, 5 cm, and 8 cm.
What type of triangle is this tile?
5 cm, 5 cm, 8 cm
Look at the three side lengths: 5 cm, 5 cm, and 8 cm
Step 1 of 3
Lucy is sorting triangular tiles for an art project. One tile has sides measuring 5 cm, 5 cm, and 8 cm.
What type of triangle is this tile?
The tile is an isosceles triangle because it has exactly 2 equal sides.
The key insight: Count the matching sides: 3 equal = equilateral, 2 equal = isosceles, 0 equal = scalene!
Common mix-up: Calling it equilateral because two sides match. Equilateral means ALL three sides are equal, not just two.
These are the misconceptions we see most often in classify triangles, including the ones our practice questions are specifically designed to catch.
Struggling with classify triangles? The real gap is often in one of these earlier topics.
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