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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 802 · 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.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 29° and 26°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 24° and angle B = 47°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 28° and 21°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 25° and angle B = 81°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  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.In triangle ABC, angle A = 25° and angle B = 130°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 61° and angle B = 48°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 59° and angle B = 55°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  19. 19.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)?
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  21. 21.Can a triangle have sides of 2 cm, 12 cm and 8 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 4 cm, 8 cm and 12 cm? (a) Yes (b) No
  23. 23.Can a triangle have sides of 11 cm, 9 cm and 8 cm? (a) Yes (b) No
  24. 24.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)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 22° and angle B = 50°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 19 cm and 9 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 18 cm, 7 cm and 7 cm? (a) Yes (b) No
  31. 31.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 24° and 69°. What is the exterior angle (in degrees)?
  33. 33.Can a triangle have sides of 10 cm, 2 cm and 9 cm? (a) Yes (b) No
  34. 34.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  35. 35.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 100° and angle B = 30°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 10 cm and 8 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 4 cm, 10 cm and 16 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 24 cm, 7 cm and 12 cm? (a) No (b) Yes
  40. 40.The two interior opposite angles of a triangle are 66° and 46°. What is the exterior angle (in degrees)?

Answer key

  1. 40
  2. 26
  3. 26
  4. 58
  5. 23
  6. 55
  7. 109
  8. 62
  9. 49
  10. 74
  11. 90
  12. 15
  13. 25
  14. 44
  15. 71
  16. 66
  17. 36
  18. 45
  19. 24
  20. 100
  21. No
  22. No
  23. Yes
  24. 8
  25. 45
  26. 108
  27. 36
  28. 57
  29. No
  30. No
  31. 56
  32. 93
  33. Yes
  34. 28
  35. 60
  36. 50
  37. Yes
  38. No
  39. No
  40. 112

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