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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 933 · 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.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  4. 4.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  6. 6.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 88° and angle B = 68°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 80° and 41°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 43° and angle B = 70°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 8 cm and 2 cm? (a) No (b) Yes
  13. 13.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  14. 14.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 23° and angle B = 20°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 32° and angle B = 59°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 77° and angle B = 58°. What is angle C (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 57° and 28°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 30° and angle B = 123°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 35° and 53°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 40° and angle B = 59°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 11 cm, 17 cm and 9 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 10 cm, 7 cm and 6 cm? (a) No (b) Yes
  30. 30.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  31. 31.Can a triangle have sides of 7 cm, 12 cm and 22 cm? (a) No (b) Yes
  32. 32.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 92° and angle B = 35°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 6 cm, 14 cm and 6 cm? (a) No (b) Yes
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  39. 39.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)?
  40. 40.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?

Answer key

  1. 13
  2. 22
  3. 25
  4. 44
  5. 30
  6. 140
  7. 45
  8. 24
  9. 121
  10. 67
  11. 51
  12. Yes
  13. 24
  14. 24
  15. 54
  16. 137
  17. 89
  18. 45
  19. 85
  20. 27
  21. 52
  22. 22
  23. 88
  24. 90
  25. 90
  26. 36
  27. 81
  28. Yes
  29. Yes
  30. 25
  31. No
  32. 51
  33. 18
  34. 28
  35. 53
  36. No
  37. 10
  38. 102
  39. 8
  40. 62

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