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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 803 · 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.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  4. 4.In triangle ABC, angle A = 63° and angle B = 43°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 20 cm and 8 cm? (a) Yes (b) No
  8. 8.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)?
  9. 9.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 28° and 33°. What is the exterior angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 10 cm and 24 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 biggest angle (in degrees)?
  15. 15.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)?
  16. 16.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 22° and angle B = 71°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  23. 23.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  24. 24.Can a triangle have sides of 14 cm, 5 cm and 5 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 78° and 76°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 50° and angle B = 85°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 5 cm, 9 cm and 14 cm? (a) No (b) Yes
  30. 30.The two interior opposite angles of a triangle are 48° and 58°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 9 cm, 17 cm and 8 cm? (a) Yes (b) No
  33. 33.Can a triangle have sides of 8 cm, 8 cm and 8 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 71° and angle B = 79°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 62° and angle B = 35°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 32° and angle B = 42°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 29° and 64°. What is the exterior angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 74
  2. 100
  3. 5
  4. 74
  5. 52
  6. 59
  7. No
  8. 10
  9. 56
  10. 64
  11. 30
  12. 61
  13. 26
  14. 120
  15. 7
  16. 33
  17. 87
  18. 58
  19. 61
  20. 71
  21. 50
  22. 84
  23. 24
  24. No
  25. 60
  26. 29
  27. 154
  28. 45
  29. No
  30. 106
  31. 16
  32. No
  33. Yes
  34. 30
  35. 83
  36. 106
  37. 40
  38. 72
  39. 93
  40. 45

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