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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 645 · 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 shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 9 cm, 2 cm and 16 cm? (a) No (b) Yes
  4. 4.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 6 cm, 18 cm and 7 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 50° and 30°. What is the exterior angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 11 cm and 11 cm? (a) No (b) Yes
  11. 11.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 79° and angle B = 61°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 99° and angle B = 24°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 53° and 80°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 16 cm and 10 cm? (a) Yes (b) No
  29. 29.The two interior opposite angles of a triangle are 39° and 67°. What is the exterior angle (in degrees)?
  30. 30.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 39° and angle B = 108°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 99° and angle B = 38°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 22° and angle B = 33°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 4 cm, 8 cm and 15 cm? (a) No (b) Yes
  35. 35.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  36. 36.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  38. 38.Can a triangle have sides of 15 cm, 8 cm and 10 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?

Answer key

  1. 39
  2. 18
  3. No
  4. 54
  5. 64
  6. No
  7. 80
  8. 45
  9. 76
  10. Yes
  11. 23
  12. 120
  13. 25
  14. 18
  15. 98
  16. 48
  17. 62
  18. 40
  19. 50
  20. 69
  21. 58
  22. 57
  23. 20
  24. 133
  25. 74
  26. 40
  27. 18
  28. Yes
  29. 106
  30. 34
  31. 33
  32. 43
  33. 125
  34. No
  35. 24
  36. 100
  37. 45
  38. Yes
  39. 64
  40. 90

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