Types of triangle worksheet - Free Printable

Let’s go step by step to match each triangle shape with its correct name.

We have 5 triangles on the left and 5 names on the right. Each triangle matches only one name.

---

Triangle 1 (top):
It has two sides marked with little lines — that means those two sides are equal in length.
→ This is an Isosceles triangle (a triangle with at least two equal sides).

Wait — let’s check all before deciding. Maybe another triangle also looks isosceles? Let’s keep going.

---

Triangle 2:
All angles look sharp (less than 90°), and no sides are marked as equal. But wait — actually, looking closely, it might be equilateral? No — no tick marks. Actually, this one has all angles acute, but we need to see if any sides are equal. Since there are no tick marks, maybe it’s just a regular acute triangle? Hmm… let’s hold off.

Actually, let’s look for clearer clues first.

---

Triangle 3:
Has a small square in the corner → that means it has a right angle (90°).
→ So this must be the Right-angled triangle.

✔ Match: Triangle 3 → Right-angled triangle

---

Triangle 4:
One angle is clearly wider than 90° — it’s “blunt” or “open wide”. That’s called an obtuse angle.
→ So this is the Obtuse-angled triangle.

✔ Match: Triangle 4 → Obtuse-angled triangle

---

Triangle 5 (bottom):
All three sides have tick marks — meaning ALL THREE SIDES ARE EQUAL.
→ That’s the definition of an Equilateral triangle.

✔ Match: Triangle 5 → Equilateral triangle

---

Now back to Triangle 1 and Triangle 2.

Triangle 1: Two sides have tick marks → so two sides equal → Isosceles triangle

Triangle 2: No tick marks, all angles look less than 90° → so all angles are acute → Acute-angled triangle

That leaves us with:

- Triangle 1 → Isosceles
- Triangle 2 → Acute-angled
- Triangle 3 → Right-angled
- Triangle 4 → Obtuse-angled
- Triangle 5 → Equilateral

But wait — what about the label “Isosceles triangle”? We used it for Triangle 1. And “Equilateral” for Triangle 5. That’s fine — equilateral is a special case of isosceles, but here they’re treated separately, which is okay for this level.

Also, note: Triangle 2 doesn’t have any side markings, so we can’t say it’s isosceles or equilateral — but since all angles are acute, “Acute-angled triangle” fits perfectly.

Let’s double-check:

- Triangle 1: two equal sides → Isosceles ✔
- Triangle 2: all angles < 90° → Acute-angled ✔
- Triangle 3: has right angle → Right-angled ✔
- Triangle 4: one angle > 90° → Obtuse-angled ✔
- Triangle 5: all sides equal → Equilateral ✔

Perfect! All matched correctly.

Final Answer:
Triangle 1 → Isosceles triangle
Triangle 2 → Acute-angled triangle
Triangle 3 → Right-angled triangle
Triangle 4 → Obtuse-angled triangle
Triangle 5 → Equilateral triangle