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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 885 · 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 triangle ABC, angle A = 90° and angle B = 24°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 38° and angle B = 62°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  5. 5.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)?
  6. 6.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 38° and angle B = 49°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 2 cm, 5 cm and 4 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 65° and 26°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 21° and angle B = 123°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 68° and angle B = 83°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 3 cm, 9 cm and 14 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 9 cm, 7 cm and 9 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 60° and angle B = 61°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 11 cm and 9 cm? (a) No (b) Yes
  22. 22.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 25° and 35°. What is the exterior angle (in degrees)?
  26. 26.Can a triangle have sides of 11 cm, 7 cm and 10 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  29. 29.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)?
  30. 30.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.Can a triangle have sides of 8 cm, 4 cm and 2 cm? (a) No (b) Yes
  33. 33.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 23° and 24°. What is the exterior angle (in degrees)?
  36. 36.Can a triangle have sides of 12 cm, 5 cm and 4 cm? (a) Yes (b) No
  37. 37.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 10 cm, 5 cm and 7 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 33° and 21°. What is the exterior angle (in degrees)?

Answer key

  1. 66
  2. 28
  3. 80
  4. 20
  5. 36
  6. 39
  7. 26
  8. 80
  9. 100
  10. 93
  11. Yes
  12. 43
  13. 91
  14. 36
  15. 29
  16. No
  17. 70
  18. 134
  19. Yes
  20. 59
  21. Yes
  22. 92
  23. 48
  24. 71
  25. 60
  26. Yes
  27. 76
  28. 86
  29. 15
  30. 8
  31. 36
  32. No
  33. 17
  34. 20
  35. 47
  36. No
  37. 24
  38. Yes
  39. 65
  40. 54

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