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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 438 · 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.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  2. 2.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 79° and 44°. What is the exterior angle (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 7 cm and 12 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 40° and 25°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 8 cm, 5 cm and 7 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 67° and angle B = 21°. What is angle C (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  13. 13.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)?
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 26° and angle B = 94°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  24. 24.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 3 cm, 11 cm and 18 cm? (a) Yes (b) No
  28. 28.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 80° and angle B = 27°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 44° and 52°. What is the exterior angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 70° and 22°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 55° and angle B = 100°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 57° and 63°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  38. 38.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)?
  39. 39.The two interior opposite angles of a triangle are 58° and 32°. What is the exterior angle (in degrees)?
  40. 40.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?

Answer key

  1. 100
  2. 28
  3. 123
  4. Yes
  5. 120
  6. 18
  7. 44
  8. 65
  9. Yes
  10. 14
  11. 92
  12. 26
  13. 15
  14. 45
  15. 15
  16. 54
  17. 110
  18. 60
  19. 47
  20. 72
  21. 25
  22. 30
  23. 36
  24. 27
  25. 67
  26. 22
  27. No
  28. 54
  29. Yes
  30. 73
  31. 96
  32. 92
  33. 25
  34. 61
  35. 138
  36. 120
  37. 78
  38. 24
  39. 90
  40. 33

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