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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 723 · 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 12 cm, 22 cm and 6 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 12 cm, 9 cm and 9 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 45° and angle B = 38°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 94° and angle B = 53°. What is angle C (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  7. 7.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  8. 8.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 4 cm, 10 cm and 13 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 31° and 73°. What is the exterior angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 56° and 59°. What is the exterior angle (in degrees)?
  13. 13.In triangle ABC, angle A = 70° and angle B = 83°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 88° and angle B = 29°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 35° and angle B = 58°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 12 cm, 12 cm and 4 cm? (a) No (b) Yes
  20. 20.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  27. 27.Can a triangle have sides of 5 cm, 5 cm and 5 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 71° and angle B = 46°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 8 cm, 8 cm and 5 cm? (a) No (b) Yes
  30. 30.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  32. 32.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 75° and 30°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 31° and angle B = 72°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 60° and 68°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?

Answer key

  1. No
  2. Yes
  3. 97
  4. 64
  5. 33
  6. 13
  7. 72
  8. 45
  9. 13
  10. Yes
  11. 104
  12. 115
  13. 27
  14. 63
  15. 87
  16. 51
  17. 74
  18. 53
  19. Yes
  20. 24
  21. 31
  22. 32
  23. 32
  24. 34
  25. 25
  26. 17
  27. Yes
  28. 63
  29. Yes
  30. 74
  31. 33
  32. 5
  33. 105
  34. 77
  35. 128
  36. 46
  37. 26
  38. 70
  39. 66
  40. 25

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