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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 574 · 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 = 21° and angle B = 22°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  5. 5.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  6. 6.Can a triangle have sides of 21 cm, 11 cm and 8 cm? (a) Yes (b) No
  7. 7.In triangle ABC, angle A = 52° and angle B = 77°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 40° and 33°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 44° and angle B = 81°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 58° and 27°. What is the exterior angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 43° and 49°. What is the exterior angle (in degrees)?
  16. 16.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 89° and angle B = 50°. What is angle C (in degrees)?
  19. 19.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)?
  20. 20.In triangle ABC, angle A = 39° and angle B = 101°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  22. 22.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  23. 23.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)?
  24. 24.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)?
  25. 25.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 8 cm and 4 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 45° and angle B = 78°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 14 cm, 11 cm and 9 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 47° and angle B = 68°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 74° and 53°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 8 cm, 7 cm and 13 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 71° and 76°. What is the exterior angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  40. 40.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?

Answer key

  1. 137
  2. 66
  3. 13
  4. 60
  5. 70
  6. No
  7. 51
  8. 72
  9. 73
  10. 70
  11. 55
  12. 134
  13. 85
  14. 66
  15. 92
  16. 66
  17. 40
  18. 41
  19. 7
  20. 40
  21. 120
  22. 8
  23. 18
  24. 12
  25. 58
  26. 68
  27. Yes
  28. 57
  29. Yes
  30. 65
  31. 55
  32. 127
  33. 19
  34. Yes
  35. 147
  36. 48
  37. 23
  38. 45
  39. 25
  40. 72

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