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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 510 · 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 6 cm. How long is the third side (in cm)?
  2. 2.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 58° and angle B = 80°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 23° and angle B = 52°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 3 cm, 8 cm and 8 cm? (a) No (b) Yes
  7. 7.Can a triangle have sides of 9 cm, 25 cm and 12 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 6 cm, 2 cm and 7 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 54° and angle B = 79°. What is angle C (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 41° and 33°. What is the exterior angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 30°. What is the other one (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.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 44° and angle B = 102°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  23. 23.Can a triangle have sides of 4 cm, 21 cm and 12 cm? (a) Yes (b) No
  24. 24.The two interior opposite angles of a triangle are 67° and 24°. What is the exterior angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  26. 26.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 43° and 55°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 35° and 54°. What is the exterior angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  36. 36.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)?
  37. 37.Can a triangle have sides of 9 cm, 9 cm and 4 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 37° and angle B = 31°. What is angle C (in degrees)?

Answer key

  1. 8
  2. 36
  3. 46
  4. 42
  5. 105
  6. Yes
  7. No
  8. 76
  9. 12
  10. 90
  11. 49
  12. 42
  13. Yes
  14. 47
  15. 74
  16. 59
  17. 55
  18. 80
  19. 24
  20. 51
  21. 34
  22. 90
  23. No
  24. 91
  25. 75
  26. 70
  27. 25
  28. 98
  29. 48
  30. 58
  31. 36
  32. 17
  33. 80
  34. 89
  35. 24
  36. 8
  37. Yes
  38. 80
  39. 54
  40. 112

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