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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 930 · 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.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  3. 3.Can a triangle have sides of 5 cm, 7 cm and 6 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 7 cm, 16 cm and 6 cm? (a) Yes (b) No
  5. 5.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  6. 6.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)?
  7. 7.The two interior opposite angles of a triangle are 69° and 77°. What is the exterior angle (in degrees)?
  8. 8.In triangle ABC, angle A = 99° and angle B = 27°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 13 cm, 6 cm and 2 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 9 cm, 14 cm and 4 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 71° and angle B = 39°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 45°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 27° and 36°. What is the exterior angle (in degrees)?
  17. 17.In triangle ABC, angle A = 94° and angle B = 29°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 12 cm, 21 cm and 7 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 24° and angle B = 81°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 12 cm, 3 cm and 15 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 22° and angle B = 114°. 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.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  25. 25.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 72° and 58°. What is the exterior angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  28. 28.Can a triangle have sides of 7 cm, 12 cm and 9 cm? (a) No (b) Yes
  29. 29.The two interior opposite angles of a triangle are 54° and 43°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 47° and angle B = 54°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  33. 33.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  35. 35.Can a triangle have sides of 9 cm, 9 cm and 4 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  37. 37.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)?
  38. 38.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  39. 39.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 7 cm and 7 cm? (a) No (b) Yes

Answer key

  1. 75
  2. 36
  3. Yes
  4. No
  5. 55
  6. 8
  7. 146
  8. 54
  9. 20
  10. 76
  11. No
  12. 55
  13. No
  14. 70
  15. 23
  16. 63
  17. 57
  18. No
  19. 78
  20. 75
  21. No
  22. 44
  23. 40
  24. 54
  25. 34
  26. 130
  27. 25
  28. Yes
  29. 97
  30. 47
  31. 79
  32. 66
  33. 29
  34. 40
  35. Yes
  36. 61
  37. 15
  38. 36
  39. 94
  40. Yes

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