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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 75 · 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 130°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 69° and angle B = 27°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 30° and 26°. What is the exterior angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 74° and 21°. What is the exterior angle (in degrees)?
  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 40°. What is the third angle (in degrees)?
  9. 9.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  10. 10.In triangle ABC, angle A = 65° and angle B = 64°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 67° and 59°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 80° and 45°. What is the exterior angle (in degrees)?
  17. 17.In triangle ABC, angle A = 27° and angle B = 34°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 31° and angle B = 23°. What is angle C (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 31° and 76°. What is the exterior angle (in degrees)?
  23. 23.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  24. 24.In triangle ABC, angle A = 53° and angle B = 39°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  26. 26.Can a triangle have sides of 24 cm, 11 cm and 10 cm? (a) Yes (b) No
  27. 27.Can a triangle have sides of 17 cm, 7 cm and 5 cm? (a) No (b) Yes
  28. 28.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  29. 29.In triangle ABC, angle A = 58° and angle B = 71°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 70° and angle B = 30°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 67° and angle B = 35°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 37° and angle B = 76°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 80° and angle B = 54°. What is angle C (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 36° and angle B = 99°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?

Answer key

  1. 70
  2. 68
  3. 84
  4. 90
  5. 56
  6. 95
  7. 36
  8. 50
  9. 9
  10. 51
  11. 68
  12. 90
  13. 34
  14. 126
  15. 80
  16. 125
  17. 119
  18. 12
  19. 37
  20. 54
  21. 126
  22. 107
  23. 10
  24. 88
  25. 72
  26. No
  27. No
  28. 7
  29. 51
  30. 80
  31. 34
  32. 78
  33. 67
  34. 46
  35. 106
  36. 45
  37. 72
  38. 10
  39. 55
  40. 33

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