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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 862 · 40 sums
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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 93°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 77° and angle B = 56°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 23 cm, 9 cm and 11 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 69° and 62°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 30° and angle B = 113°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  8. 8.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)?
  9. 9.The two interior opposite angles of a triangle are 29° and 65°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 38° and angle B = 32°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  16. 16.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 40° and 47°. What is the exterior angle (in degrees)?
  18. 18.Can a triangle have sides of 7 cm, 6 cm and 6 cm? (a) No (b) Yes
  19. 19.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 53° and angle B = 61°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 39° and angle B = 74°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 11 cm, 7 cm and 10 cm? (a) Yes (b) No
  31. 31.Can a triangle have sides of 6 cm, 6 cm and 3 cm? (a) No (b) Yes
  32. 32.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 47° and angle B = 33°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  36. 36.Can a triangle have sides of 5 cm, 15 cm and 9 cm? (a) No (b) Yes
  37. 37.The two interior opposite angles of a triangle are 64° and 57°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  39. 39.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 6 cm, 2 cm and 7 cm? (a) No (b) Yes

Answer key

  1. 71
  2. 72
  3. 47
  4. No
  5. 131
  6. 37
  7. 77
  8. 15
  9. 94
  10. 11
  11. 76
  12. 110
  13. 10
  14. 20
  15. 13
  16. 27
  17. 87
  18. Yes
  19. 50
  20. 66
  21. 80
  22. 116
  23. 58
  24. 67
  25. 73
  26. 38
  27. 45
  28. 28
  29. 79
  30. Yes
  31. Yes
  32. 57
  33. 100
  34. 100
  35. 90
  36. No
  37. 121
  38. 84
  39. 80
  40. Yes

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