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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 335 · 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 a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 63° and 22°. What is the exterior angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 29° and 53°. What is the exterior angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  10. 10.Can a triangle have sides of 5 cm, 4 cm and 5 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 35° and angle B = 40°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 42° and 33°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 83° and angle B = 35°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 24° and angle B = 114°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 38° and angle B = 63°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 32° and angle B = 126°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 88° and angle B = 58°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 5 cm, 3 cm and 3 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 55° and angle B = 49°. What is angle C (in degrees)?
  28. 28.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  29. 29.In triangle ABC, angle A = 22° and angle B = 24°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  32. 32.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 57° and angle B = 66°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 5 cm and 2 cm? (a) Yes (b) No
  38. 38.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  39. 39.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?

Answer key

  1. 24
  2. 85
  3. 72
  4. 17
  5. 47
  6. 59
  7. 82
  8. 30
  9. 48
  10. Yes
  11. 72
  12. 105
  13. 77
  14. 75
  15. 62
  16. 22
  17. 65
  18. 42
  19. 79
  20. 22
  21. 80
  22. 34
  23. 80
  24. 16
  25. 48
  26. Yes
  27. 76
  28. 24
  29. 134
  30. 40
  31. 25
  32. 30
  33. 79
  34. 43
  35. 106
  36. 57
  37. No
  38. 22
  39. 32
  40. 61

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