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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 759 · 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 = 87° and angle B = 39°. What is angle C (in degrees)?
  2. 2.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  3. 3.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  5. 5.The two interior opposite angles of a triangle are 36° and 60°. What is the exterior angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  8. 8.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 35° and angle B = 32°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 79° and angle B = 26°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 94° and angle B = 31°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  19. 19.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 4 cm and 19 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 39° and angle B = 75°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 8 cm and 20 cm? (a) Yes (b) No
  26. 26.The two interior opposite angles of a triangle are 26° and 80°. What is the exterior angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 77° and 47°. What is the exterior angle (in degrees)?
  30. 30.Can a triangle have sides of 6 cm, 3 cm and 8 cm? (a) No (b) Yes
  31. 31.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  32. 32.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 52° and 35°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 34° and 30°. What is the exterior angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 64° and angle B = 55°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 36° and 46°. What is the exterior angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 21° and 24°. What is the exterior angle (in degrees)?

Answer key

  1. 54
  2. 15
  3. 53
  4. 17
  5. 96
  6. 15
  7. 41
  8. 73
  9. 113
  10. 72
  11. 47
  12. 50
  13. 112
  14. 11
  15. 72
  16. 75
  17. 55
  18. 40
  19. 59
  20. 44
  21. 64
  22. No
  23. 66
  24. 79
  25. No
  26. 106
  27. 90
  28. 6
  29. 124
  30. Yes
  31. 42
  32. 52
  33. 87
  34. 64
  35. 50
  36. 61
  37. 82
  38. 4
  39. 36
  40. 45

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