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.

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Step 1: Look at the first triangle (top left)
It has two small lines (tick marks) on two of its sides. That means those two sides are equal in length.
→ This is an isosceles triangle.
*(Isosceles = two equal sides)*

But wait — let’s check all shapes before assigning, because we must make sure each name is used only once.

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Step 2: Second triangle from top
No tick marks, no right angle symbol. All angles look less than 90° (sharp corners).
→ This could be an acute-angled triangle (all angles < 90°).

Hold on — let’s keep going.

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Step 3: Third triangle from top
Has a square symbol in the corner → that means it’s a right angle (90°).
→ So this is definitely a right-angled triangle.

✔ Match confirmed: third shape → Right-angled triangle

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Step 4: Fourth triangle from top
Looks like one angle is wider than 90° (obtuse). No tick marks, no right angle.
→ This is an obtuse-angled triangle.

✔ Match: fourth shape → Obtuse-angled triangle

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Step 5: Fifth triangle (bottom left)
Has tick marks on ALL THREE sides → meaning all three sides are equal.
→ This is an equilateral triangle.

✔ Match: fifth shape → Equilateral triangle

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Now go back to the first triangle:
It had tick marks on TWO sides → so it’s isosceles.

Then the second triangle (second from top):
No special marks, but since we’ve already matched:
- equilateral (all sides equal)
- isosceles (two sides equal)
- right-angled (has 90°)
- obtuse-angled (one angle > 90°)

That leaves acute-angled triangle for the second shape — which makes sense because all its angles appear to be less than 90°, and it doesn’t fit any other category.

Wait — actually, let’s double-check:

The first triangle (with two tick marks) → isosceles
The fifth triangle (with three tick marks) → equilateral
The third triangle (with right angle box) → right-angled
The fourth triangle (wide angle) → obtuse-angled
The second triangle (no marks, all sharp angles) → acute-angled

Yes — that uses all five names correctly.

So final matching:

1. First triangle (two tick marks) → Isosceles triangle
2. Second triangle (plain, all acute angles) → Acute-angled triangle
3. Third triangle (right angle symbol) → Right-angled triangle
4. Fourth triangle (one wide angle) → Obtuse-angled triangle
5. Fifth triangle (three tick marks) → Equilateral triangle

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Final Answer:
First triangle → Isosceles triangle
Second triangle → Acute-angled triangle
Third triangle → Right-angled triangle
Fourth triangle → Obtuse-angled triangle
Fifth triangle → Equilateral triangle