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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 392 · 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 angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  4. 4.Can a triangle have sides of 4 cm, 7 cm and 7 cm? (a) No (b) Yes
  5. 5.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  6. 6.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  8. 8.The two interior opposite angles of a triangle are 33° and 63°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 4 cm, 6 cm and 5 cm? (a) No (b) Yes
  10. 10.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 11 cm and 18 cm? (a) No (b) Yes
  12. 12.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)?
  13. 13.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 72° and angle B = 48°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 8 cm and 20 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  26. 26.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  27. 27.In triangle ABC, angle A = 77° and angle B = 23°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 14 cm and 4 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 7 cm, 3 cm and 14 cm? (a) Yes (b) No
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  33. 33.Can a triangle have sides of 7 cm, 13 cm and 3 cm? (a) No (b) Yes
  34. 34.The two interior opposite angles of a triangle are 28° and 21°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 43° and angle B = 20°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 79° and angle B = 29°. What is angle C (in degrees)?

Answer key

  1. 80
  2. 66
  3. 38
  4. Yes
  5. 70
  6. 78
  7. 17
  8. 96
  9. Yes
  10. 20
  11. No
  12. 15
  13. 12
  14. 65
  15. 26
  16. 90
  17. 60
  18. 16
  19. 66
  20. 68
  21. No
  22. 18
  23. 31
  24. 25
  25. 66
  26. 38
  27. 80
  28. 64
  29. 60
  30. No
  31. No
  32. 25
  33. No
  34. 49
  35. 117
  36. 72
  37. 70
  38. 77
  39. 74
  40. 72

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