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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 741 · 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 an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 52° and 46°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 34° and 79°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  7. 7.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 35° and angle B = 25°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  13. 13.In triangle ABC, angle A = 22° and angle B = 129°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 14 cm, 5 cm and 6 cm? (a) Yes (b) No
  15. 15.Can a triangle have sides of 4 cm, 4 cm and 4 cm? (a) Yes (b) No
  16. 16.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  19. 19.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 72° and angle B = 68°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 38° and angle B = 102°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 16 cm, 3 cm and 8 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  28. 28.Can a triangle have sides of 3 cm, 12 cm and 11 cm? (a) Yes (b) No
  29. 29.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 85° and angle B = 59°. What is angle C (in degrees)?
  31. 31.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  35. 35.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 72° and angle B = 54°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 41° and angle B = 54°. What is angle C (in degrees)?

Answer key

  1. 60
  2. 55
  3. 98
  4. 113
  5. 104
  6. 23
  7. 21
  8. 50
  9. 90
  10. 100
  11. 120
  12. 20
  13. 29
  14. No
  15. Yes
  16. 66
  17. 69
  18. 17
  19. 66
  20. 30
  21. 40
  22. 40
  23. 28
  24. 15
  25. 80
  26. No
  27. 20
  28. Yes
  29. 54
  30. 36
  31. 24
  32. 20
  33. 54
  34. 12
  35. 72
  36. 50
  37. 54
  38. 78
  39. 82
  40. 85

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