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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 512 · 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 95°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 66° and angle B = 59°. What is angle C (in degrees)?
  4. 4.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)?
  5. 5.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 6 cm, 20 cm and 9 cm? (a) No (b) Yes
  7. 7.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)?
  8. 8.Can a triangle have sides of 9 cm, 5 cm and 9 cm? (a) Yes (b) No
  9. 9.The two interior opposite angles of a triangle are 41° and 30°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 22° and angle B = 109°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 92° and angle B = 32°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 71° and angle B = 64°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 37° and 47°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  29. 29.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 32° and angle B = 49°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 64° and 23°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 38° and angle B = 75°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 21° and angle B = 66°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 73° and angle B = 72°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 5 cm, 3 cm and 7 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 41° and 59°. What is the exterior angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  39. 39.The two interior opposite angles of a triangle are 52° and 47°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?

Answer key

  1. 28
  2. 36
  3. 55
  4. 15
  5. 60
  6. No
  7. 8
  8. Yes
  9. 71
  10. 26
  11. 56
  12. 59
  13. 49
  14. 30
  15. 33
  16. 25
  17. 37
  18. 56
  19. 90
  20. 56
  21. 50
  22. 18
  23. 45
  24. 84
  25. 69
  26. 54
  27. 20
  28. 26
  29. 50
  30. 99
  31. 87
  32. 67
  33. 93
  34. 35
  35. 50
  36. Yes
  37. 100
  38. 4
  39. 99
  40. 46

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