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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 607 · 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 68°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  2. 2.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 37° and angle B = 48°. What is angle C (in degrees)?
  4. 4.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  5. 5.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.Can a triangle have sides of 7 cm, 6 cm and 3 cm? (a) No (b) Yes
  7. 7.Can a triangle have sides of 17 cm, 7 cm and 7 cm? (a) No (b) Yes
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 89° and angle B = 45°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 2 cm, 5 cm and 6 cm? (a) No (b) Yes
  14. 14.Can a triangle have sides of 6 cm, 6 cm and 6 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 11 cm, 3 cm and 12 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 78° and angle B = 60°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 22° and angle B = 98°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 5 cm, 10 cm and 10 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  24. 24.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)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  26. 26.An exterior angle of a triangle is 50°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  33. 33.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 34° and angle B = 110°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 23° and angle B = 24°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 71° and 41°. What is the exterior angle (in degrees)?
  38. 38.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  39. 39.Can a triangle have sides of 14 cm, 8 cm and 3 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 44° and angle B = 40°. What is angle C (in degrees)?

Answer key

  1. 45
  2. 52
  3. 95
  4. 12
  5. 39
  6. Yes
  7. No
  8. 40
  9. 46
  10. 68
  11. 67
  12. 46
  13. Yes
  14. Yes
  15. Yes
  16. 42
  17. 45
  18. 80
  19. 60
  20. Yes
  21. 42
  22. 78
  23. 17
  24. 15
  25. 80
  26. 29
  27. 16
  28. 45
  29. 26
  30. 90
  31. 18
  32. 8
  33. 41
  34. 36
  35. 133
  36. 72
  37. 112
  38. 73
  39. No
  40. 96

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