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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 253 · 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 = 29° and angle B = 88°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 5 cm, 6 cm and 15 cm? (a) No (b) Yes
  3. 3.Can a triangle have sides of 2 cm, 2 cm and 2 cm? (a) No (b) Yes
  4. 4.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 36° and angle B = 62°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 95° and angle B = 29°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 40° and angle B = 36°. What is angle C (in degrees)?
  15. 15.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)?
  16. 16.Can a triangle have sides of 15 cm, 9 cm and 11 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 30° and 63°. What is the exterior angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 79° and 65°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 75° and angle B = 23°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 10 cm, 10 cm and 3 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 5 cm, 9 cm and 7 cm? (a) No (b) Yes
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?

Answer key

  1. 63
  2. No
  3. Yes
  4. 68
  5. 82
  6. 56
  7. 77
  8. 25
  9. 74
  10. 31
  11. 50
  12. 18
  13. 38
  14. 104
  15. 15
  16. Yes
  17. 24
  18. 32
  19. 120
  20. 17
  21. 40
  22. 93
  23. 144
  24. 70
  25. 31
  26. 18
  27. 40
  28. 50
  29. 12
  30. 46
  31. 23
  32. 23
  33. 100
  34. 80
  35. 48
  36. 82
  37. 55
  38. Yes
  39. Yes
  40. 84

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