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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 762 · 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.Can a triangle have sides of 8 cm, 3 cm and 5 cm? (a) No (b) Yes
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 25° and 29°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  11. 11.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 8 cm, 3 cm and 8 cm? (a) No (b) Yes
  14. 14.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 58° and angle B = 31°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 3 cm and 6 cm? (a) No (b) Yes
  17. 17.An exterior angle of a triangle is 49°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 29° and angle B = 49°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  29. 29.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 54° and angle B = 39°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 69° and angle B = 42°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 6 cm, 2 cm and 6 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 10 cm, 4 cm and 17 cm? (a) Yes (b) No
  36. 36.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  37. 37.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  38. 38.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  39. 39.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?

Answer key

  1. No
  2. 40
  3. 54
  4. 76
  5. 17
  6. 84
  7. 25
  8. 34
  9. 20
  10. 49
  11. 32
  12. 16
  13. Yes
  14. 51
  15. 91
  16. Yes
  17. 20
  18. 92
  19. 32
  20. 90
  21. 74
  22. 46
  23. 50
  24. 50
  25. 102
  26. 16
  27. 10
  28. 12
  29. 26
  30. 87
  31. 69
  32. 41
  33. Yes
  34. 17
  35. No
  36. 58
  37. 8
  38. 9
  39. 10
  40. 49

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