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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 837 · 40 sums
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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.

NameDateTime takenScore ___ / 40
  1. 1.The two interior opposite angles of a triangle are 47° 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.In triangle ABC, angle A = 98° and angle B = 29°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  5. 5.Can a triangle have sides of 3 cm, 11 cm and 15 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 13 cm and 3 cm? (a) Yes (b) No
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 40° and angle B = 61°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 78° and angle B = 35°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 8 cm, 5 cm and 17 cm? (a) Yes (b) No
  18. 18.In triangle ABC, angle A = 90° and angle B = 54°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 76° and angle B = 67°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 87° and angle B = 26°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 56° and angle B = 30°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 54° and angle B = 56°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 10 cm, 5 cm and 5 cm? (a) Yes (b) No
  27. 27.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 23° and angle B = 42°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  30. 30.Can a triangle have sides of 15 cm, 5 cm and 12 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 37° and angle B = 105°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 96° and angle B = 37°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 26° and angle B = 129°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 77° and angle B = 54°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 56° and angle B = 66°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 152°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?

Answer key

  1. 126
  2. 90
  3. 53
  4. 70
  5. No
  6. 33
  7. No
  8. 80
  9. 90
  10. 8
  11. 59
  12. 13
  13. 79
  14. 37
  15. 58
  16. 67
  17. No
  18. 36
  19. 124
  20. 37
  21. 67
  22. 94
  23. 30
  24. 84
  25. 70
  26. No
  27. 68
  28. 115
  29. 67
  30. Yes
  31. 38
  32. 63
  33. 47
  34. 25
  35. 36
  36. 49
  37. 58
  38. 40
  39. 80
  40. 14

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