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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 68 · 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 130°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 27° and 69°. What is the exterior angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 47° and 32°. What is the exterior angle (in degrees)?
  10. 10.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 2 cm and 11 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 81° and angle B = 54°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 49° and angle B = 53°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 2 cm, 8 cm and 13 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 11 cm, 23 cm and 8 cm? (a) No (b) Yes
  21. 21.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)?
  22. 22.Can a triangle have sides of 6 cm, 2 cm and 7 cm? (a) No (b) Yes
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 77° and angle B = 26°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  26. 26.In triangle ABC, angle A = 98° and angle B = 46°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  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 11 cm, 16 cm and 6 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 38° and angle B = 92°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 23 cm and 11 cm? (a) No (b) Yes
  35. 35.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 20 cm, 12 cm and 3 cm? (a) Yes (b) No
  37. 37.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 77° and angle B = 78°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?

Answer key

  1. 56
  2. 26
  3. 17
  4. 40
  5. 21
  6. 25
  7. 68
  8. 96
  9. 79
  10. 25
  11. Yes
  12. 45
  13. 78
  14. 90
  15. 66
  16. No
  17. 15
  18. 41
  19. 46
  20. No
  21. 10
  22. Yes
  23. 25
  24. 77
  25. 13
  26. 36
  27. 25
  28. 54
  29. Yes
  30. 50
  31. 110
  32. 33
  33. 45
  34. No
  35. 74
  36. No
  37. 23
  38. 26
  39. 25
  40. 38

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