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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 41 · 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 two interior opposite angles of a triangle are 80° and 34°. What is the exterior angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 98° and angle B = 42°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  7. 7.Can a triangle have sides of 16 cm, 3 cm and 11 cm? (a) Yes (b) No
  8. 8.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 15 cm, 4 cm and 7 cm? (a) No (b) Yes
  11. 11.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 10 cm, 22 cm and 10 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 10 cm, 3 cm and 7 cm? (a) No (b) Yes
  14. 14.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 4 cm, 12 cm and 3 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  18. 18.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  19. 19.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 88° and angle B = 30°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 49° and angle B = 21°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 11 cm, 7 cm and 20 cm? (a) No (b) Yes
  24. 24.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  26. 26.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  27. 27.Can a triangle have sides of 8 cm, 11 cm and 20 cm? (a) Yes (b) No
  28. 28.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 11 cm and 21 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 75° and 28°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 50° and 25°. What is the exterior angle (in degrees)?
  36. 36.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 28° and 25°. What is the exterior angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?

Answer key

  1. 114
  2. 70
  3. 40
  4. 40
  5. 35
  6. 25
  7. No
  8. 77
  9. 73
  10. No
  11. 36
  12. No
  13. No
  14. 112
  15. 86
  16. No
  17. 37
  18. 12
  19. 28
  20. 62
  21. 110
  22. 82
  23. No
  24. 72
  25. 52
  26. 7
  27. No
  28. 43
  29. 19
  30. No
  31. 65
  32. 103
  33. 38
  34. 60
  35. 75
  36. 43
  37. 56
  38. 53
  39. 64
  40. 118

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