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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 641 · 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 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)?
  2. 2.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 35° and angle B = 58°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  5. 5.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 9 cm and 9 cm? (a) No (b) Yes
  8. 8.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)?
  9. 9.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  10. 10.In triangle ABC, angle A = 100° and angle B = 51°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 90° and angle B = 60°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  16. 16.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)?
  17. 17.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 7 cm and 3 cm? (a) Yes (b) No
  19. 19.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 25° and 74°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 93° and angle B = 27°. What is angle C (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 22° and 36°. What is the exterior angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 38° and 30°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 62° and angle B = 24°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 42° and angle B = 44°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 22 cm and 6 cm? (a) Yes (b) No
  29. 29.The two interior opposite angles of a triangle are 25° and 47°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 46° and 30°. What is the exterior angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 25° and 25°. What is the exterior angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 35° and 28°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 7 cm, 10 cm and 20 cm? (a) Yes (b) No
  35. 35.An exterior angle of a triangle is 44°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 43° and angle B = 47°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?

Answer key

  1. 24
  2. 73
  3. 87
  4. 25
  5. 69
  6. 100
  7. Yes
  8. 8
  9. 3
  10. 29
  11. 30
  12. 50
  13. 80
  14. 36
  15. 33
  16. 36
  17. 78
  18. Yes
  19. 40
  20. 99
  21. 60
  22. 58
  23. 102
  24. 63
  25. 68
  26. 94
  27. 94
  28. No
  29. 72
  30. 76
  31. 84
  32. 50
  33. 63
  34. No
  35. 21
  36. 38
  37. 90
  38. 27
  39. 90
  40. 53

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