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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 522 · 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.In triangle ABC, angle A = 37° and angle B = 53°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 70° and 23°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 99° and angle B = 59°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 6 cm and 6 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 84° and angle B = 26°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 3 cm, 10 cm and 7 cm? (a) No (b) Yes
  12. 12.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 41° and angle B = 73°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 51° and 40°. What is the exterior angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  20. 20.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 99° and angle B = 28°. What is angle C (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 angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  26. 26.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 50° and angle B = 66°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 78° and 80°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 35° and angle B = 27°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 11 cm, 10 cm and 26 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 41° and angle B = 104°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 25° and angle B = 116°. What is angle C (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 44° and 40°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  38. 38.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 80° and angle B = 45°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?

Answer key

  1. 90
  2. 51
  3. 49
  4. 93
  5. 72
  6. 7
  7. 46
  8. 22
  9. Yes
  10. 70
  11. No
  12. 27
  13. 66
  14. 66
  15. 40
  16. 72
  17. 21
  18. 91
  19. 10
  20. 36
  21. 53
  22. 36
  23. 45
  24. 25
  25. 39
  26. Yes
  27. 64
  28. 158
  29. 80
  30. 118
  31. 70
  32. No
  33. 35
  34. 39
  35. 12
  36. 84
  37. 22
  38. 29
  39. 55
  40. 58

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