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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 685 · 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 40° and 25°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 95° and angle B = 42°. What is angle C (in degrees)?
  3. 3.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  4. 4.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 78° and 63°. What is the exterior angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 79° and 45°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 5 cm, 6 cm and 2 cm? (a) Yes (b) No
  10. 10.The two interior opposite angles of a triangle are 24° and 42°. What is the exterior angle (in degrees)?
  11. 11.Can a triangle have sides of 3 cm, 4 cm and 2 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 7 cm, 6 cm and 2 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 48° and angle B = 95°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 69° and angle B = 61°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  18. 18.Can a triangle have sides of 7 cm, 12 cm and 5 cm? (a) No (b) Yes
  19. 19.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 7 cm, 7 cm and 8 cm? (a) No (b) Yes
  21. 21.The two interior opposite angles of a triangle are 70° and 32°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 60° and 73°. What is the exterior angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  27. 27.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  29. 29.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 32° and angle B = 20°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 50° and 47°. What is the exterior angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 17 cm, 4 cm and 12 cm? (a) No (b) Yes
  40. 40.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?

Answer key

  1. 65
  2. 43
  3. 12
  4. 92
  5. 141
  6. 124
  7. 17
  8. 24
  9. Yes
  10. 66
  11. Yes
  12. Yes
  13. 86
  14. 37
  15. 50
  16. 8
  17. 20
  18. No
  19. 73
  20. Yes
  21. 102
  22. 37
  23. 118
  24. 36
  25. 133
  26. 26
  27. 39
  28. 13
  29. 28
  30. 128
  31. 75
  32. 60
  33. 61
  34. 98
  35. 97
  36. 120
  37. 90
  38. 73
  39. No
  40. 10

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