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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 388 · 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.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  5. 5.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  15. 15.Can a triangle have sides of 9 cm, 3 cm and 7 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 6 cm, 13 cm and 6 cm? (a) No (b) Yes
  17. 17.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 53° and angle B = 42°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  23. 23.Can a triangle have sides of 3 cm, 16 cm and 12 cm? (a) No (b) Yes
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 65° and angle B = 30°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 58° and angle B = 48°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 20 cm, 8 cm and 10 cm? (a) No (b) Yes
  30. 30.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 37° and 72°. What is the exterior angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 99° and angle B = 34°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 22° and angle B = 81°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 61° and angle B = 77°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 70° and angle B = 26°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 5 cm, 6 cm and 10 cm? (a) Yes (b) No
  40. 40.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?

Answer key

  1. 45
  2. 40
  3. 77
  4. 18
  5. 62
  6. 50
  7. 74
  8. 27
  9. 66
  10. 48
  11. 36
  12. 59
  13. 17
  14. 10
  15. Yes
  16. No
  17. 80
  18. 20
  19. 20
  20. 85
  21. 30
  22. 45
  23. No
  24. 25
  25. 85
  26. 74
  27. 48
  28. 116
  29. No
  30. 67
  31. 109
  32. 41
  33. 28
  34. 47
  35. 77
  36. 42
  37. 84
  38. 34
  39. Yes
  40. 32

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