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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 105 · 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 64°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 15 cm, 6 cm and 9 cm? (a) Yes (b) No
  3. 3.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 67° and angle B = 23°. What is angle C (in degrees)?
  5. 5.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  6. 6.Can a triangle have sides of 11 cm, 3 cm and 13 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 38° and angle B = 43°. What is angle C (in degrees)?
  8. 8.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 34° and angle B = 110°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 12 cm, 7 cm and 24 cm? (a) Yes (b) No
  13. 13.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 6 cm and 16 cm? (a) No (b) Yes
  19. 19.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 65° and angle B = 39°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  22. 22.Can a triangle have sides of 7 cm, 10 cm and 8 cm? (a) No (b) Yes
  23. 23.The two interior opposite angles of a triangle are 69° and 55°. What is the exterior angle (in degrees)?
  24. 24.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 3 cm, 3 cm and 11 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 33° and angle B = 122°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 17 cm, 7 cm and 7 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 12 cm, 3 cm and 11 cm? (a) Yes (b) No
  31. 31.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  32. 32.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 57° and 24°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 47° and angle B = 68°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 21 cm, 9 cm and 9 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 9 cm, 9 cm and 10 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 4 cm, 8 cm and 9 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 41° and angle B = 40°. What is angle C (in degrees)?

Answer key

  1. 44
  2. No
  3. 32
  4. 90
  5. 24
  6. Yes
  7. 99
  8. 15
  9. 90
  10. 58
  11. 36
  12. No
  13. 40
  14. 96
  15. 50
  16. 64
  17. 138
  18. No
  19. 46
  20. 76
  21. 10
  22. Yes
  23. 124
  24. 22
  25. 48
  26. 40
  27. No
  28. 25
  29. No
  30. Yes
  31. 19
  32. 64
  33. 79
  34. 81
  35. 65
  36. No
  37. Yes
  38. Yes
  39. 128
  40. 99

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