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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 591 · 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 144°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  2. 2.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  4. 4.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 51° and angle B = 32°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 11 cm, 25 cm and 9 cm? (a) Yes (b) No
  8. 8.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 49° and 22°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 42° and 26°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 12 cm and 6 cm? (a) No (b) Yes
  20. 20.Can a triangle have sides of 6 cm, 5 cm and 2 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  23. 23.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 45° and angle B = 35°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 5 cm, 4 cm and 7 cm? (a) Yes (b) No
  29. 29.In triangle ABC, angle A = 92° and angle B = 61°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 20 cm, 7 cm and 11 cm? (a) Yes (b) No
  34. 34.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)?
  35. 35.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 17 cm, 6 cm and 8 cm? (a) No (b) Yes
  37. 37.The two interior opposite angles of a triangle are 21° and 46°. What is the exterior angle (in degrees)?
  38. 38.Can a triangle have sides of 5 cm, 3 cm and 11 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 32° and angle B = 115°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 86° and angle B = 24°. What is angle C (in degrees)?

Answer key

  1. 66
  2. 20
  3. 26
  4. 77
  5. 20
  6. 97
  7. No
  8. 47
  9. 71
  10. 26
  11. 39
  12. 64
  13. 29
  14. 34
  15. 68
  16. 132
  17. 90
  18. 27
  19. Yes
  20. Yes
  21. 17
  22. 60
  23. 24
  24. 16
  25. 20
  26. 100
  27. 45
  28. Yes
  29. 27
  30. 58
  31. 64
  32. 74
  33. No
  34. 15
  35. 29
  36. No
  37. 67
  38. No
  39. 33
  40. 70

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