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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 650 · 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 an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 54° and 69°. What is the exterior angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 15 cm and 2 cm? (a) No (b) Yes
  9. 9.Can a triangle have sides of 10 cm, 12 cm and 20 cm? (a) No (b) Yes
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  11. 11.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.Can a triangle have sides of 6 cm, 4 cm and 12 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 9 cm, 7 cm and 6 cm? (a) Yes (b) No
  15. 15.In triangle ABC, angle A = 21° and angle B = 127°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 20 cm and 10 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  18. 18.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)?
  19. 19.The two interior opposite angles of a triangle are 23° and 39°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 50° and angle B = 33°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 82° and angle B = 40°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 6 cm and 12 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 21 cm, 6 cm and 11 cm? (a) No (b) Yes
  28. 28.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 71° and 66°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 73° and angle B = 26°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 92° and angle B = 20°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 11 cm, 6 cm and 9 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 83° and angle B = 23°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  39. 39.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  40. 40.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?

Answer key

  1. 69
  2. 34
  3. 40
  4. 123
  5. 39
  6. 72
  7. 84
  8. No
  9. Yes
  10. 26
  11. 94
  12. 40
  13. No
  14. Yes
  15. 32
  16. Yes
  17. 70
  18. 8
  19. 62
  20. 71
  21. 97
  22. 54
  23. 37
  24. 58
  25. 17
  26. Yes
  27. No
  28. 19
  29. 75
  30. 137
  31. 44
  32. 81
  33. 15
  34. 68
  35. 10
  36. Yes
  37. 74
  38. 37
  39. 56
  40. 70

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