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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 178 · 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 angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 43° and 59°. What is the exterior angle (in degrees)?
  4. 4.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 36° and angle B = 82°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 40° and angle B = 23°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 45° and 65°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 6 cm, 12 cm and 16 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 33° and angle B = 75°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  12. 12.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  13. 13.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)?
  14. 14.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 58° and 30°. What is the exterior angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 85° and angle B = 60°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 61° and angle B = 53°. What is angle C (in degrees)?
  20. 20.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  21. 21.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  23. 23.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)?
  24. 24.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 68° and angle B = 26°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 56° and angle B = 38°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 6 cm, 9 cm and 4 cm? (a) No (b) Yes
  33. 33.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 88° and angle B = 56°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 72° and angle B = 45°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 5 cm, 8 cm and 14 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 24 cm, 9 cm and 12 cm? (a) No (b) Yes
  40. 40.Can a triangle have sides of 5 cm, 6 cm and 4 cm? (a) Yes (b) No

Answer key

  1. 70
  2. 46
  3. 102
  4. 75
  5. 62
  6. 117
  7. 30
  8. 110
  9. Yes
  10. 72
  11. 84
  12. 51
  13. 20
  14. 39
  15. 88
  16. 80
  17. 44
  18. 35
  19. 66
  20. 24
  21. 71
  22. 36
  23. 24
  24. 17
  25. 31
  26. 20
  27. 86
  28. 46
  29. 34
  30. 53
  31. 86
  32. Yes
  33. 60
  34. 90
  35. 45
  36. 36
  37. 63
  38. No
  39. No
  40. Yes

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