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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 34 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  5. 5.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 38° and angle B = 117°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 8 cm and 4 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 57° and 77°. What is the exterior angle (in degrees)?
  12. 12.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  13. 13.Can a triangle have sides of 4 cm, 4 cm and 13 cm? (a) Yes (b) No
  14. 14.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  15. 15.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  16. 16.In triangle ABC, angle A = 22° and angle B = 136°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 11 cm, 3 cm and 11 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 93° and angle B = 49°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 8 cm, 3 cm and 10 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 6 cm and 2 cm? (a) Yes (b) No
  25. 25.Can a triangle have sides of 8 cm, 9 cm and 18 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 31° and angle B = 114°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 5 cm and 12 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 56° and angle B = 34°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  32. 32.Can a triangle have sides of 11 cm, 9 cm and 9 cm? (a) No (b) Yes
  33. 33.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  34. 34.In triangle ABC, angle A = 95° and angle B = 62°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 28° and angle B = 32°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 7 cm, 6 cm and 10 cm? (a) Yes (b) No
  37. 37.In triangle ABC, angle A = 64° and angle B = 81°. What is angle C (in degrees)?
  38. 38.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  39. 39.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  40. 40.In triangle ABC, angle A = 62° and angle B = 89°. What is angle C (in degrees)?

Answer key

  1. 112
  2. 27
  3. 45
  4. 52
  5. 42
  6. 32
  7. 25
  8. 75
  9. 84
  10. No
  11. 134
  12. 36
  13. No
  14. 25
  15. 17
  16. 22
  17. 40
  18. 41
  19. Yes
  20. 38
  21. 57
  22. Yes
  23. 138
  24. Yes
  25. No
  26. 35
  27. Yes
  28. 90
  29. 68
  30. 42
  31. 72
  32. Yes
  33. 10
  34. 23
  35. 120
  36. Yes
  37. 35
  38. 15
  39. 5
  40. 29

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