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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 443 · 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.The two interior opposite angles of a triangle are 44° and 80°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 97° and angle B = 47°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  7. 7.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)?
  8. 8.In triangle ABC, angle A = 71° and angle B = 78°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 41° and 34°. What is the exterior angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  14. 14.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 28° and angle B = 81°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 9 cm, 9 cm and 15 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 10 cm, 17 cm and 9 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 48° and 50°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  26. 26.In triangle ABC, angle A = 61° and angle B = 21°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 68° and angle B = 35°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 35° and 27°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 60° and 40°. What is the exterior angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  34. 34.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 25° and angle B = 108°. What is angle C (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  37. 37.Can a triangle have sides of 10 cm, 5 cm and 17 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 9 cm, 19 cm and 8 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?

Answer key

  1. 124
  2. 60
  3. 39
  4. 36
  5. 30
  6. 18
  7. 8
  8. 31
  9. 50
  10. 75
  11. 75
  12. 69
  13. 33
  14. 50
  15. 86
  16. 70
  17. 46
  18. 78
  19. 71
  20. Yes
  21. Yes
  22. 71
  23. 98
  24. 17
  25. 25
  26. 98
  27. 77
  28. 62
  29. 40
  30. 100
  31. 30
  32. 57
  33. 20
  34. 36
  35. 47
  36. 17
  37. No
  38. No
  39. 67
  40. 25

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