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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 697 · 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.In triangle ABC, angle A = 83° and angle B = 62°. What is angle C (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 76° and 20°. What is the exterior angle (in degrees)?
  4. 4.Can a triangle have sides of 13 cm, 8 cm and 5 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 6 cm, 9 cm and 3 cm? (a) No (b) Yes
  8. 8.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 11 cm, 20 cm and 8 cm? (a) Yes (b) No
  10. 10.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 57° and angle B = 39°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 6 cm, 9 cm and 12 cm? (a) Yes (b) No
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 33° and angle B = 119°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 42° and angle B = 95°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 27° and 76°. What is the exterior angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 29° and 35°. What is the exterior angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  26. 26.Can a triangle have sides of 3 cm, 4 cm and 3 cm? (a) No (b) Yes
  27. 27.The two interior opposite angles of a triangle are 29° and 73°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  29. 29.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)?
  30. 30.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (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.The two interior opposite angles of a triangle are 68° and 62°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  38. 38.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  39. 39.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?

Answer key

  1. 35
  2. 25
  3. 96
  4. No
  5. 56
  6. 20
  7. No
  8. 32
  9. No
  10. 72
  11. 78
  12. 84
  13. Yes
  14. 20
  15. 75
  16. 11
  17. 48
  18. 28
  19. 90
  20. 19
  21. 29
  22. 43
  23. 103
  24. 64
  25. 72
  26. Yes
  27. 102
  28. 74
  29. 15
  30. 45
  31. 65
  32. 24
  33. 94
  34. 42
  35. 130
  36. 130
  37. 5
  38. 16
  39. 33
  40. 16

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