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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 433 · 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.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 87° and angle B = 60°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 25° and angle B = 40°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 69° and angle B = 30°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 15 cm, 10 cm and 12 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 63° and angle B = 32°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 51° and angle B = 65°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 42° and angle B = 62°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 28° and angle B = 42°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 2 cm and 14 cm? (a) Yes (b) No
  17. 17.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 45° and 26°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 62° and 46°. What is the exterior angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  24. 24.The two interior opposite angles of a triangle are 53° and 65°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 29° and angle B = 68°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 79° and angle B = 56°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 36° and angle B = 29°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  30. 30.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)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 20° and 41°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 5 cm and 2 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?

Answer key

  1. 24
  2. 33
  3. 115
  4. 40
  5. 81
  6. Yes
  7. 85
  8. 69
  9. 45
  10. 64
  11. 51
  12. 76
  13. 90
  14. 110
  15. 10
  16. No
  17. 26
  18. 130
  19. 71
  20. 66
  21. 72
  22. 108
  23. 26
  24. 118
  25. 83
  26. 45
  27. 115
  28. 78
  29. 20
  30. 8
  31. 33
  32. 61
  33. 55
  34. No
  35. 12
  36. 20
  37. 42
  38. 50
  39. 22
  40. 124

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