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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 69 · 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 = 72° and angle B = 84°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 35° and 28°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  11. 11.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)?
  12. 12.Can a triangle have sides of 17 cm, 8 cm and 6 cm? (a) No (b) Yes
  13. 13.The two interior opposite angles of a triangle are 51° and 49°. What is the exterior angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  15. 15.Can a triangle have sides of 6 cm, 12 cm and 5 cm? (a) Yes (b) No
  16. 16.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 94° and angle B = 62°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  22. 22.Can a triangle have sides of 9 cm, 3 cm and 7 cm? (a) Yes (b) No
  23. 23.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)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 9 cm, 6 cm and 9 cm? (a) Yes (b) No
  27. 27.In triangle ABC, angle A = 65° and angle B = 26°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 8 cm and 20 cm? (a) Yes (b) No
  29. 29.Can a triangle have sides of 3 cm, 2 cm and 4 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 58° and angle B = 86°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 64° and angle B = 53°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  33. 33.In triangle ABC, angle A = 76° and angle B = 69°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  35. 35.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)?
  36. 36.In triangle ABC, angle A = 22° and angle B = 118°. What is angle C (in degrees)?
  37. 37.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  38. 38.In triangle ABC, angle A = 30° and angle B = 35°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 31° and angle B = 69°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 50° and angle B = 35°. What is angle C (in degrees)?

Answer key

  1. 24
  2. 63
  3. 50
  4. 118
  5. 18
  6. 48
  7. 34
  8. 64
  9. 48
  10. 72
  11. 36
  12. No
  13. 100
  14. 17
  15. No
  16. 17
  17. 24
  18. 72
  19. 25
  20. 40
  21. 76
  22. Yes
  23. 7
  24. 30
  25. 60
  26. Yes
  27. 89
  28. No
  29. Yes
  30. 36
  31. 63
  32. 50
  33. 35
  34. 44
  35. 8
  36. 40
  37. 18
  38. 115
  39. 80
  40. 95

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