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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 49 · 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 78° and 68°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  6. 6.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 20° and 24°. What is the exterior angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 23° and angle B = 23°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 52°. What is the other one (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.Can a triangle have sides of 7 cm, 7 cm and 19 cm? (a) No (b) Yes
  17. 17.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 72° and angle B = 24°. What is angle C (in degrees)?
  20. 20.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)?
  21. 21.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 89° and angle B = 24°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 11 cm, 5 cm and 12 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 23° and angle B = 133°. What is angle C (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 8 cm, 4 cm and 17 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 99° and angle B = 20°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 21° and angle B = 114°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 2 cm, 5 cm and 4 cm? (a) Yes (b) No
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.The two interior opposite angles of a triangle are 61° and 75°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 48° and angle B = 92°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 25° and 80°. What is the exterior angle (in degrees)?

Answer key

  1. 146
  2. 53
  3. 10
  4. 61
  5. 30
  6. 82
  7. 50
  8. 79
  9. 44
  10. 6
  11. 44
  12. 134
  13. 20
  14. 21
  15. 26
  16. No
  17. 78
  18. 24
  19. 84
  20. 15
  21. 51
  22. 46
  23. 57
  24. 67
  25. 43
  26. Yes
  27. 90
  28. 24
  29. 60
  30. No
  31. 61
  32. 42
  33. 45
  34. Yes
  35. 25
  36. 136
  37. 40
  38. 18
  39. 56
  40. 105

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