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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 66 · 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.The two interior opposite angles of a triangle are 66° and 61°. What is the exterior angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  4. 4.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)?
  5. 5.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 9 cm, 9 cm and 23 cm? (a) Yes (b) No
  7. 7.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 31° and angle B = 35°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 30° and 44°. What is the exterior angle (in degrees)?
  13. 13.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 63° and angle B = 57°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 8 cm and 17 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 94° and angle B = 31°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 52° and angle B = 20°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 88° and angle B = 50°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 89° and angle B = 31°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 6 cm and 11 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 14 cm, 7 cm and 2 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  28. 28.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  29. 29.In triangle ABC, angle A = 26° and angle B = 66°. What is angle C (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  31. 31.In triangle ABC, angle A = 40° and angle B = 65°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 76° and 80°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 77° and angle B = 66°. What is angle C (in degrees)?
  35. 35.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)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 20° and angle B = 54°. What is angle C (in degrees)?

Answer key

  1. 127
  2. 21
  3. 104
  4. 12
  5. 80
  6. No
  7. 13
  8. 114
  9. 36
  10. 60
  11. 20
  12. 74
  13. 69
  14. 60
  15. No
  16. 78
  17. 55
  18. 108
  19. 45
  20. 42
  21. 60
  22. Yes
  23. 14
  24. 16
  25. 36
  26. No
  27. 90
  28. 39
  29. 88
  30. 10
  31. 75
  32. 77
  33. 156
  34. 37
  35. 15
  36. 61
  37. 17
  38. 35
  39. 70
  40. 106

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