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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 272 · 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 1 : 3 : 5. What is the biggest angle (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 20 cm and 9 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 64° and angle B = 94°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 32° and angle B = 94°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 57° and 56°. What is the exterior angle (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 17 cm and 4 cm? (a) Yes (b) No
  8. 8.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 96° and angle B = 29°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 20° and 50°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 22° and angle B = 126°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 20° and 32°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  25. 25.Can a triangle have sides of 3 cm, 9 cm and 11 cm? (a) No (b) Yes
  26. 26.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 33° and 47°. What is the exterior angle (in degrees)?
  32. 32.Can a triangle have sides of 8 cm, 13 cm and 5 cm? (a) Yes (b) No
  33. 33.Can a triangle have sides of 10 cm, 9 cm and 8 cm? (a) No (b) Yes
  34. 34.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  35. 35.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  36. 36.The two interior opposite angles of a triangle are 30° and 36°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  39. 39.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?

Answer key

  1. 100
  2. No
  3. 36
  4. 22
  5. 54
  6. 113
  7. No
  8. 70
  9. 20
  10. 74
  11. 55
  12. 70
  13. 80
  14. 13
  15. 11
  16. 75
  17. 120
  18. 32
  19. 56
  20. 20
  21. 40
  22. 54
  23. 52
  24. 70
  25. Yes
  26. 72
  27. 132
  28. 20
  29. 60
  30. 75
  31. 80
  32. No
  33. Yes
  34. 33
  35. 6
  36. 66
  37. 56
  38. 14
  39. 27
  40. 74

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