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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 739 · 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.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 53° and angle B = 49°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 16 cm, 12 cm and 5 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  6. 6.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)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 11 cm, 7 cm and 22 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 24° and angle B = 54°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 71° and angle B = 86°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 80° and 34°. What is the exterior angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 57° and 38°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 70° and 26°. What is the exterior angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 55° and 28°. What is the exterior angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 33° and 46°. What is the exterior angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 21° and 60°. What is the exterior angle (in degrees)?
  24. 24.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 68° and 78°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 35° and angle B = 31°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 11 cm, 4 cm and 20 cm? (a) No (b) Yes
  28. 28.The two interior opposite angles of a triangle are 35° and 48°. What is the exterior angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 73° and 72°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 63° and angle B = 51°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 21° and 80°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 77° and angle B = 51°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 6 cm, 5 cm and 3 cm? (a) Yes (b) No
  36. 36.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 9 cm, 7 cm and 12 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  39. 39.Can a triangle have sides of 11 cm, 8 cm and 8 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?

Answer key

  1. 29
  2. 78
  3. 78
  4. Yes
  5. 28
  6. 24
  7. 36
  8. 27
  9. No
  10. 68
  11. 102
  12. 23
  13. 32
  14. 114
  15. 95
  16. 14
  17. 96
  18. 40
  19. 40
  20. 83
  21. 24
  22. 79
  23. 81
  24. 28
  25. 146
  26. 114
  27. No
  28. 83
  29. 145
  30. 52
  31. 90
  32. 66
  33. 101
  34. 52
  35. Yes
  36. 17
  37. Yes
  38. 72
  39. Yes
  40. 80

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