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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 564 · 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.Can a triangle have sides of 18 cm, 10 cm and 10 cm? (a) Yes (b) No
  2. 2.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  3. 3.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 57° and 60°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 90° and angle B = 34°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 33° and 69°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 82° and angle B = 38°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 5 cm, 9 cm and 16 cm? (a) No (b) Yes
  13. 13.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 23° and 26°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 70° and angle B = 28°. What is angle C (in degrees)?
  20. 20.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)?
  21. 21.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  23. 23.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 3 cm and 17 cm? (a) Yes (b) No
  26. 26.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 31° and 51°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 74° and 50°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 10 cm, 9 cm and 21 cm? (a) No (b) Yes
  32. 32.Can a triangle have sides of 4 cm, 10 cm and 4 cm? (a) Yes (b) No
  33. 33.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 55° and angle B = 42°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 50° and angle B = 20°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 32° and 67°. What is the exterior angle (in degrees)?

Answer key

  1. Yes
  2. 24
  3. 37
  4. 70
  5. 8
  6. 117
  7. 56
  8. 90
  9. 80
  10. 102
  11. 60
  12. No
  13. 22
  14. 35
  15. 118
  16. 49
  17. 64
  18. 21
  19. 82
  20. 15
  21. 76
  22. 29
  23. 31
  24. 10
  25. No
  26. 58
  27. 45
  28. 120
  29. 82
  30. 124
  31. No
  32. No
  33. 35
  34. 42
  35. 83
  36. 110
  37. 32
  38. 57
  39. 70
  40. 99

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