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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 344 · 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.Can a triangle have sides of 8 cm, 8 cm and 19 cm? (a) No (b) Yes
  2. 2.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  3. 3.Can a triangle have sides of 6 cm, 11 cm and 4 cm? (a) No (b) Yes
  4. 4.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 75° and angle B = 41°. What is angle C (in degrees)?
  8. 8.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  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.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  11. 11.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  13. 13.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 90° and angle B = 66°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  16. 16.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  17. 17.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 80° and angle B = 76°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.Can a triangle have sides of 11 cm, 5 cm and 7 cm? (a) No (b) Yes
  22. 22.Can a triangle have sides of 2 cm, 14 cm and 11 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 87° and angle B = 64°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  28. 28.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)?
  29. 29.In triangle ABC, angle A = 38° and angle B = 34°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 87° and angle B = 57°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 14 cm, 4 cm and 7 cm? (a) Yes (b) No
  34. 34.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 23° and 61°. 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.Can a triangle have sides of 12 cm, 3 cm and 20 cm? (a) Yes (b) No
  38. 38.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. No
  2. 37
  3. No
  4. 73
  5. 15
  6. 58
  7. 64
  8. 8
  9. 48
  10. 18
  11. 44
  12. 25
  13. 12
  14. 24
  15. 63
  16. 9
  17. 80
  18. 30
  19. 24
  20. 54
  21. Yes
  22. No
  23. 70
  24. 5
  25. 29
  26. 61
  27. 90
  28. 3
  29. 108
  30. 65
  31. 29
  32. 36
  33. No
  34. 90
  35. 84
  36. 15
  37. No
  38. 60
  39. 90
  40. 17

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