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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 328 · 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 a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 88° and angle B = 55°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 24° and 31°. What is the exterior angle (in degrees)?
  8. 8.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 64° and angle B = 48°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 43° and angle B = 28°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 49° and 35°. What is the exterior angle (in degrees)?
  13. 13.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 65° and angle B = 30°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  17. 17.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 82° and angle B = 60°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 13 cm, 4 cm and 8 cm? (a) Yes (b) No
  23. 23.The two interior opposite angles of a triangle are 60° and 73°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 30° and angle B = 77°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 10 cm, 12 cm and 22 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 8 cm, 15 cm and 12 cm? (a) No (b) Yes
  28. 28.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  30. 30.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  31. 31.The two interior opposite angles of a triangle are 56° and 36°. What is the exterior angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 42° and angle B = 74°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  36. 36.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 12 cm, 10 cm and 22 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 41° and angle B = 92°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 88° and angle B = 44°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 29° and angle B = 38°. What is angle C (in degrees)?

Answer key

  1. 67
  2. 48
  3. 16
  4. 37
  5. 90
  6. 94
  7. 55
  8. 77
  9. 68
  10. 109
  11. 40
  12. 84
  13. 55
  14. 85
  15. 126
  16. 17
  17. 130
  18. 59
  19. 38
  20. 44
  21. 54
  22. No
  23. 133
  24. 140
  25. 73
  26. No
  27. Yes
  28. 79
  29. 30
  30. 8
  31. 92
  32. 13
  33. 64
  34. 62
  35. 90
  36. 64
  37. No
  38. 47
  39. 48
  40. 113

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