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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 576 · 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 angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  4. 4.In triangle ABC, angle A = 41° and angle B = 78°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 87° and angle B = 64°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 3 cm, 6 cm and 5 cm? (a) Yes (b) No
  8. 8.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 35° and 32°. What is the exterior angle (in degrees)?
  10. 10.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 4 cm, 4 cm and 8 cm? (a) Yes (b) No
  12. 12.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 23° and angle B = 23°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 24 cm, 11 cm and 10 cm? (a) Yes (b) No
  16. 16.The two interior opposite angles of a triangle are 63° and 79°. What is the exterior angle (in degrees)?
  17. 17.Can a triangle have sides of 23 cm, 10 cm and 10 cm? (a) No (b) Yes
  18. 18.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 42° and angle B = 26°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  24. 24.An exterior angle of a triangle is 151°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 83° and angle B = 43°. What is angle C (in degrees)?
  26. 26.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  27. 27.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  29. 29.In triangle ABC, angle A = 43° and angle B = 76°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 38° and angle B = 34°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  36. 36.Can a triangle have sides of 5 cm, 12 cm and 7 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 5 cm, 16 cm and 6 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 6 cm, 9 cm and 6 cm? (a) No (b) Yes
  39. 39.In triangle ABC, angle A = 75° and angle B = 34°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?

Answer key

  1. 24
  2. 25
  3. 45
  4. 61
  5. 29
  6. 51
  7. Yes
  8. 74
  9. 67
  10. 42
  11. No
  12. 78
  13. 35
  14. 134
  15. No
  16. 142
  17. No
  18. 110
  19. 70
  20. 45
  21. 112
  22. 90
  23. 25
  24. 79
  25. 54
  26. 24
  27. 72
  28. 36
  29. 61
  30. 108
  31. 36
  32. 41
  33. 39
  34. 59
  35. 38
  36. No
  37. No
  38. Yes
  39. 71
  40. 64

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