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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 553 · 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 two interior opposite angles of a triangle are 31° and 79°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  6. 6.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  7. 7.In triangle ABC, angle A = 25° and angle B = 92°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 74° and angle B = 37°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  13. 13.Can a triangle have sides of 11 cm, 8 cm and 18 cm? (a) No (b) Yes
  14. 14.The two interior opposite angles of a triangle are 44° and 71°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 30° and angle B = 102°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 37° and 78°. What is the exterior angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 13 cm and 10 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 38° and angle B = 59°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  27. 27.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)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 50° and angle B = 33°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 80° and 40°. What is the exterior angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  34. 34.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 30° and angle B = 41°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 71° and angle B = 33°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 26° and 24°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?

Answer key

  1. 110
  2. 90
  3. 15
  4. 67
  5. 48
  6. 15
  7. 63
  8. 27
  9. 74
  10. 69
  11. 32
  12. 90
  13. Yes
  14. 115
  15. 90
  16. 48
  17. 48
  18. 115
  19. 76
  20. 84
  21. Yes
  22. 83
  23. 70
  24. 66
  25. 17
  26. 71
  27. 15
  28. 60
  29. 110
  30. 97
  31. 120
  32. 31
  33. 4
  34. 77
  35. 109
  36. 76
  37. 19
  38. 64
  39. 50
  40. 62

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