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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 164 · 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 longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 6 cm, 4 cm and 7 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 60° and angle B = 76°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  9. 9.Can a triangle have sides of 15 cm, 6 cm and 4 cm? (a) Yes (b) No
  10. 10.The two interior opposite angles of a triangle are 79° and 26°. What is the exterior angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 32° and 44°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 4 cm, 11 cm and 8 cm? (a) Yes (b) No
  13. 13.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  15. 15.Can a triangle have sides of 10 cm, 11 cm and 2 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 70° and 24°. What is the exterior angle (in degrees)?
  19. 19.In triangle ABC, angle A = 63° and angle B = 81°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 5 cm and 6 cm? (a) Yes (b) No
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  24. 24.In triangle ABC, angle A = 31° and angle B = 73°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  26. 26.Can a triangle have sides of 22 cm, 11 cm and 9 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 27° and angle B = 44°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 72° and angle B = 28°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  32. 32.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 43° and angle B = 80°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 59° and 42°. What is the exterior angle (in degrees)?
  36. 36.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)?
  37. 37.In triangle ABC, angle A = 84° and angle B = 26°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 62° and 24°. What is the exterior angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 22° and 80°. What is the exterior angle (in degrees)?

Answer key

  1. 10
  2. 54
  3. 15
  4. Yes
  5. 116
  6. 44
  7. 106
  8. 70
  9. No
  10. 105
  11. 76
  12. Yes
  13. 70
  14. 73
  15. Yes
  16. 23
  17. 30
  18. 94
  19. 36
  20. 75
  21. Yes
  22. 72
  23. 59
  24. 76
  25. 27
  26. No
  27. 80
  28. 109
  29. 80
  30. 90
  31. 3
  32. 25
  33. 54
  34. 57
  35. 101
  36. 15
  37. 70
  38. 86
  39. 36
  40. 102

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