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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 405 · 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 4 : 5 : 6. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 76° and angle B = 52°. What is angle C (in degrees)?
  3. 3.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  4. 4.The two interior opposite angles of a triangle are 58° and 47°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 24° and angle B = 128°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 24° and angle B = 51°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 92° and angle B = 33°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 29° and 25°. What is the exterior angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 52° and angle B = 83°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 5 cm, 5 cm and 2 cm? (a) No (b) Yes
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  14. 14.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 8 cm and 8 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 72° and angle B = 67°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 5 cm, 3 cm and 5 cm? (a) No (b) Yes
  20. 20.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 8 cm, 4 cm and 5 cm? (a) Yes (b) No
  22. 22.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  25. 25.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  26. 26.An exterior angle of a triangle is 49°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 84° and angle B = 35°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 3 cm, 3 cm and 6 cm? (a) Yes (b) No
  30. 30.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 64° and 51°. What is the exterior angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 68° and angle B = 74°. 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.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 59° and angle B = 61°. What is angle C (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?

Answer key

  1. 48
  2. 52
  3. 15
  4. 105
  5. 90
  6. 28
  7. 105
  8. 55
  9. 54
  10. 80
  11. 45
  12. Yes
  13. 10
  14. 67
  15. Yes
  16. 41
  17. 28
  18. 38
  19. Yes
  20. 63
  21. Yes
  22. 75
  23. 20
  24. 64
  25. 29
  26. 27
  27. 48
  28. 61
  29. No
  30. 34
  31. 115
  32. 4
  33. 72
  34. 18
  35. 40
  36. 38
  37. 37
  38. 17
  39. 60
  40. 72

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