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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 545 · 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 two equal angles are 32° each. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  4. 4.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  5. 5.In triangle ABC, angle A = 83° and angle B = 52°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 32° and angle B = 83°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 37° and angle B = 93°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 24 cm, 11 cm and 8 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 66° and angle B = 50°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 86° and angle B = 28°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 78° and angle B = 47°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 43° and angle B = 59°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 38° and angle B = 39°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 77° and angle B = 73°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 32° and angle B = 127°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 41° and angle B = 111°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  28. 28.The two interior opposite angles of a triangle are 52° and 46°. What is the exterior angle (in degrees)?
  29. 29.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 79° and angle B = 57°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 26° and angle B = 89°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 50° and 77°. What is the exterior angle (in degrees)?
  36. 36.Can a triangle have sides of 10 cm, 12 cm and 5 cm? (a) No (b) Yes
  37. 37.The two interior opposite angles of a triangle are 32° and 73°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 43° and angle B = 116°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?

Answer key

  1. 116
  2. 10
  3. 25
  4. 12
  5. 45
  6. 65
  7. 36
  8. 50
  9. 48
  10. No
  11. 64
  12. 71
  13. 66
  14. 55
  15. 79
  16. 134
  17. 78
  18. 103
  19. 30
  20. 20
  21. 21
  22. 70
  23. 72
  24. 104
  25. 28
  26. 75
  27. 12
  28. 98
  29. 58
  30. 44
  31. 58
  32. 65
  33. 21
  34. 37
  35. 127
  36. Yes
  37. 105
  38. 72
  39. 21
  40. 17

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