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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 749 · 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.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.Can a triangle have sides of 3 cm, 11 cm and 3 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 81° and angle B = 24°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  8. 8.In triangle ABC, angle A = 92° and angle B = 67°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  11. 11.Can a triangle have sides of 14 cm, 7 cm and 3 cm? (a) Yes (b) No
  12. 12.The two interior opposite angles of a triangle are 39° and 20°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 99° and angle B = 37°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 73° and angle B = 43°. What is angle C (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 68° and 26°. What is the exterior angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  24. 24.Can a triangle have sides of 2 cm, 13 cm and 11 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 27° and angle B = 23°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 69° and angle B = 64°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  29. 29.An exterior angle of a triangle is 148°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  30. 30.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 23 cm, 10 cm and 10 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 41° and angle B = 49°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  36. 36.In triangle ABC, angle A = 66° and angle B = 53°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 54° and angle B = 41°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 75° and angle B = 78°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?

Answer key

  1. 20
  2. 26
  3. 30
  4. 17
  5. No
  6. 75
  7. 29
  8. 21
  9. 45
  10. 10
  11. No
  12. 59
  13. 45
  14. 41
  15. 44
  16. 64
  17. 94
  18. 20
  19. 84
  20. 12
  21. 104
  22. 53
  23. 120
  24. No
  25. 130
  26. 28
  27. 47
  28. 29
  29. 77
  30. 5
  31. 78
  32. No
  33. 90
  34. 36
  35. 51
  36. 61
  37. 85
  38. 100
  39. 27
  40. 28

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