G3c - The sum of angles in a triangle and the angle properties of ... - Free Printable

Let’s solve each triangle one by one using the rule:
Angles in a triangle always add up to 180°.

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First Triangle (with angle a°):
We are given two angles: 70° and 50°.
So,
a° = 180° - 70° - 50°
a° = 60°

✔ Check: 70 + 50 + 60 = 180 → Correct.

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Second Triangle (with angle b°):
Given angles: 42° and 62°.
So,
b° = 180° - 42° - 62°
b° = 76°

✔ Check: 42 + 62 + 76 = 180 → Correct.

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Third Triangle (with angle c°):
This is a right-angled triangle (see the square symbol — that means 90°).
Also, the two legs have tick marks — meaning they are equal length → so it’s an isosceles right triangle.
That means the two non-right angles are equal.

So we have:
- One angle = 90°
- The other two angles are equal → let’s call each of them c°

Then:
c° + c° + 90° = 180°
2c° = 90°
c° = 45°

✔ Check: 45 + 45 + 90 = 180 → Correct.

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Final Answer:
a = 60, b = 76, c = 45