Let’s solve each triangle step by step.
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Triangle 1 (top left):
We know two angles: 45° and 70°.
The sum of all angles in a triangle is always 180°.
So, missing angle x = 180° - 45° - 70°
→ x = 65°
✔ Check: 45 + 70 + 65 = 180 → Correct.
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Triangle 2 (top right):
One angle is 110°, and the other two are both labeled “x” — meaning they’re equal.
So: x + x + 110° = 180°
→ 2x = 180° - 110° = 70°
→ x = 35°
✔ Check: 35 + 35 + 110 = 180 → Correct.
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Triangle 3 (bottom left):
This one has an exterior angle marked as “x”, and inside the triangle we have angles y and 51°, and another angle 62°.
First, find angle y inside the triangle:
Sum of interior angles = 180°
→ y + 62° + 51° = 180°
→ y = 180° - 62° - 51° = 67°
Now, angle x is the exterior angle adjacent to y.
Exterior angle + interior angle = 180° (they form a straight line)
→ x = 180° - y = 180° - 67° = 113°
✔ Check: Interior angles: 67 + 62 + 51 = 180 → Good.
Exterior x = 113°, which matches 180 - 67 → Good.
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Triangle 4 (bottom right):
We see an exterior angle of 120°, and it’s adjacent to angle x.
So, x + 120° = 180° → x = 60°
Now, inside the triangle, we have angles: 70°, y, and x (which we found is 60°).
Sum = 180° → 70° + y + 60° = 180°
→ y = 180° - 70° - 60° = 50°
✔ Check: 70 + 60 + 50 = 180 → Correct.
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Final Answers:
Top left: x = 65°
Top right: x = 35°
Bottom left: x = 113°, y = 67°
Bottom right: x = 60°, y = 50°
Final Answer:
Top left: x = 65°; Top right: x = 35°; Bottom left: x = 113°, y = 67°; Bottom right: x = 60°, y = 50°
Parent Tip: Review the logic above to help your child master the concept of triangle missing angle worksheet.
