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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 377 · 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.Can a triangle have sides of 3 cm, 8 cm and 3 cm? (a) Yes (b) No
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 18 cm, 9 cm and 9 cm? (a) Yes (b) No
  6. 6.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  8. 8.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 59° and angle B = 58°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 80° and angle B = 60°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 9 cm, 7 cm and 7 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  18. 18.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 79° and angle B = 79°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 50° and 35°. What is the exterior angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 28° and angle B = 37°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 24° and angle B = 90°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.Can a triangle have sides of 9 cm, 24 cm and 12 cm? (a) Yes (b) No
  33. 33.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  34. 34.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  36. 36.Can a triangle have sides of 10 cm, 8 cm and 3 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 85° and angle B = 46°. What is angle C (in degrees)?

Answer key

  1. No
  2. 72
  3. 45
  4. 20
  5. No
  6. 18
  7. 57
  8. 60
  9. 63
  10. 40
  11. 29
  12. 51
  13. Yes
  14. 72
  15. 26
  16. 36
  17. 67
  18. 70
  19. 84
  20. 22
  21. 42
  22. 90
  23. 62
  24. 74
  25. 90
  26. 85
  27. 20
  28. 90
  29. 115
  30. 66
  31. 24
  32. No
  33. 25
  34. 29
  35. 39
  36. Yes
  37. 64
  38. 80
  39. 48
  40. 49

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