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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 308 · 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.

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  1. 1.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  2. 2.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  3. 3.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  8. 8.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)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  11. 11.Can a triangle have sides of 3 cm, 11 cm and 9 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 74° and angle B = 26°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 48° and angle B = 71°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 32° and angle B = 108°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 41° and angle B = 53°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 58° and angle B = 22°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 33° and angle B = 81°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 42° and angle B = 74°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 75° and 31°. What is the exterior angle (in degrees)?
  26. 26.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)?
  27. 27.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 61° and angle B = 54°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 6 cm, 4 cm and 14 cm? (a) No (b) Yes
  32. 32.Can a triangle have sides of 6 cm, 16 cm and 6 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 5 cm, 7 cm and 11 cm? (a) Yes (b) No
  34. 34.The two interior opposite angles of a triangle are 77° and 68°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 8 cm, 3 cm and 4 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 42° and 20°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 70° and angle B = 23°. What is angle C (in degrees)?

Answer key

  1. 6
  2. 26
  3. 50
  4. 60
  5. 46
  6. 20
  7. 13
  8. 8
  9. 70
  10. 17
  11. Yes
  12. 80
  13. 90
  14. 72
  15. 61
  16. 40
  17. 86
  18. 100
  19. 30
  20. 15
  21. 66
  22. 64
  23. 40
  24. 90
  25. 106
  26. 15
  27. 29
  28. 65
  29. 90
  30. 15
  31. No
  32. No
  33. Yes
  34. 145
  35. 29
  36. No
  37. 62
  38. 74
  39. 34
  40. 87

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