Mon Prof Augmenté
Triangle Corners on a Ruler
Age 12 · Maths
The three corner angles of any triangle always fit together to make a straight line, which is 180°. If you know two angles of a triangle, subtract their sum from 180° to find the third angle.
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In the picture
- Red corner piece: one corner angle of the triangle.
- Blue corner piece: the second corner angle of the triangle.
- Yellow corner piece: the third corner angle of the triangle.
- Straight edge of the ruler: the three corner angles together make a straight angle of 180°.
Examples
- A triangular slice of pizza: its three corner angles add up to 180°.
- A triangular road sign: knowing two corner angles lets you find the third.
Key takeaways
- Every triangle’s three angles add to 180°.
- If two angles are known, the third is 180° minus their sum.
Quiz: Triangle Corners on a Ruler (Age 12)
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What do the three angles of any triangle add up to?
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If you know two angles of a triangle, how do you find the third angle?
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When the three angles of a triangle are placed together, what do they make?
The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.
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