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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 280 · 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 1 : 4 : 5. What is the biggest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 56° and angle B = 34°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 55° and angle B = 27°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 11 cm, 6 cm and 3 cm? (a) No (b) Yes
  5. 5.Can a triangle have sides of 15 cm, 10 cm and 4 cm? (a) No (b) Yes
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 3 cm, 19 cm and 12 cm? (a) Yes (b) No
  9. 9.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 58° and 59°. What is the exterior angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 73° and 62°. What is the exterior angle (in degrees)?
  12. 12.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 24° and 65°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  16. 16.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 92° and angle B = 50°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 14 cm, 7 cm and 7 cm? (a) No (b) Yes
  22. 22.Can a triangle have sides of 4 cm, 9 cm and 7 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 59° and angle B = 83°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 44° and angle B = 35°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  29. 29.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  31. 31.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 80° and angle B = 23°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 34° and 38°. What is the exterior angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 82° and angle B = 39°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  38. 38.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  39. 39.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 78° and angle B = 39°. What is angle C (in degrees)?

Answer key

  1. 90
  2. 90
  3. 98
  4. No
  5. No
  6. 80
  7. 45
  8. No
  9. 23
  10. 117
  11. 135
  12. 44
  13. 11
  14. 89
  15. 50
  16. 7
  17. 10
  18. 45
  19. 38
  20. 66
  21. No
  22. Yes
  23. 38
  24. 63
  25. 101
  26. 71
  27. 100
  28. 48
  29. 27
  30. 25
  31. 94
  32. 77
  33. 72
  34. 77
  35. 68
  36. 59
  37. 37
  38. 63
  39. 20
  40. 63

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