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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 497 · 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.

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  1. 1.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 71° and angle B = 70°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 42° and angle B = 39°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 94° and angle B = 45°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 41° and 25°. What is the exterior angle (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 3 cm and 2 cm? (a) Yes (b) No
  11. 11.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 4 cm and 8 cm? (a) Yes (b) No
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 77° and angle B = 77°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 87° and angle B = 65°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 83° and angle B = 39°. What is angle C (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 80° and 21°. What is the exterior angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 23° and 70°. What is the exterior angle (in degrees)?
  19. 19.In triangle ABC, angle A = 32° and angle B = 120°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 93° and angle B = 41°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 4 cm, 4 cm and 5 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 43° and angle B = 89°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 65° and angle B = 32°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  28. 28.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 3 cm and 12 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 11 cm, 15 cm and 2 cm? (a) No (b) Yes
  34. 34.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  35. 35.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 6 cm, 4 cm and 4 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 78° and angle B = 30°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 70° and angle B = 38°. What is angle C (in degrees)?

Answer key

  1. 51
  2. 26
  3. 100
  4. 39
  5. 99
  6. 24
  7. 41
  8. 36
  9. 66
  10. No
  11. 48
  12. Yes
  13. 90
  14. 26
  15. 28
  16. 58
  17. 101
  18. 93
  19. 28
  20. 74
  21. 46
  22. Yes
  23. 48
  24. 83
  25. 39
  26. 78
  27. 15
  28. 20
  29. 69
  30. 69
  31. 49
  32. Yes
  33. No
  34. 10
  35. 14
  36. Yes
  37. 72
  38. 31
  39. 98
  40. 72

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