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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 268 · 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.

NameDateTime takenScore ___ / 40
  1. 1.The two interior opposite angles of a triangle are 37° and 80°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  4. 4.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 52° and 67°. What is the exterior angle (in degrees)?
  7. 7.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 59° and 26°. What is the exterior angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 19 cm, 10 cm and 7 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 58° and 75°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 22° and angle B = 105°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (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 14°. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 47° and 36°. What is the exterior angle (in degrees)?
  17. 17.Can a triangle have sides of 10 cm, 9 cm and 5 cm? (a) Yes (b) No
  18. 18.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 55° and angle B = 75°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 95° and angle B = 43°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (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.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 56° and angle B = 35°. What is angle C (in degrees)?
  26. 26.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  30. 30.Can a triangle have sides of 13 cm, 9 cm and 4 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 47° and angle B = 45°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 49° and angle B = 31°. What is angle C (in degrees)?
  34. 34.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  35. 35.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)?
  36. 36.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 82° and angle B = 26°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  40. 40.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?

Answer key

  1. 117
  2. 65
  3. 21
  4. 40
  5. 42
  6. 119
  7. 55
  8. 85
  9. 22
  10. No
  11. 133
  12. 53
  13. 78
  14. 37
  15. 76
  16. 83
  17. Yes
  18. 116
  19. 50
  20. 48
  21. 42
  22. 18
  23. 30
  24. 120
  25. 89
  26. 73
  27. 100
  28. 25
  29. 90
  30. No
  31. 88
  32. 33
  33. 100
  34. 12
  35. 15
  36. 24
  37. 72
  38. 36
  39. 32
  40. 72

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