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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 369 · 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 angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 16 cm, 4 cm and 7 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 84° and angle B = 36°. What is angle C (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  9. 9.The two interior opposite angles of a triangle are 22° and 30°. What is the exterior angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 24° and 35°. What is the exterior angle (in degrees)?
  11. 11.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 7 cm, 5 cm and 10 cm? (a) No (b) Yes
  14. 14.In triangle ABC, angle A = 59° and angle B = 34°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 45° and angle B = 36°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  19. 19.Can a triangle have sides of 4 cm, 4 cm and 5 cm? (a) Yes (b) No
  20. 20.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  21. 21.The two interior opposite angles of a triangle are 49° and 49°. What is the exterior angle (in degrees)?
  22. 22.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  23. 23.In triangle ABC, angle A = 64° and angle B = 71°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 9 cm, 9 cm and 10 cm? (a) Yes (b) No
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 83° and angle B = 37°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 21° and angle B = 90°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 29° and angle B = 42°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 39° and angle B = 41°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  35. 35.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 77° and 33°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 69° and angle B = 63°. What is angle C (in degrees)?

Answer key

  1. 100
  2. 76
  3. 17
  4. No
  5. 24
  6. 40
  7. 60
  8. 13
  9. 52
  10. 59
  11. 12
  12. 12
  13. Yes
  14. 87
  15. 99
  16. 51
  17. 77
  18. 90
  19. Yes
  20. 10
  21. 98
  22. 20
  23. 45
  24. Yes
  25. 90
  26. 60
  27. 69
  28. 10
  29. 109
  30. 54
  31. 62
  32. 71
  33. 100
  34. 68
  35. 21
  36. 84
  37. 36
  38. 21
  39. 110
  40. 48

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