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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 151 · 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 a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 38° and angle B = 102°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  4. 4.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)?
  5. 5.In triangle ABC, angle A = 94° and angle B = 21°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.Can a triangle have sides of 10 cm, 5 cm and 11 cm? (a) No (b) Yes
  10. 10.The two interior opposite angles of a triangle are 69° and 45°. What is the exterior angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 33° and 44°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  26. 26.In triangle ABC, angle A = 92° and angle B = 51°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 47°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 65° and angle B = 82°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 69° and 28°. What is the exterior angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 88° and angle B = 42°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 72° and 72°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 15 cm, 6 cm and 6 cm? (a) Yes (b) No
  38. 38.The two interior opposite angles of a triangle are 24° and 47°. What is the exterior angle (in degrees)?
  39. 39.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)?
  40. 40.Can a triangle have sides of 7 cm, 2 cm and 9 cm? (a) No (b) Yes

Answer key

  1. 47
  2. 40
  3. 132
  4. 15
  5. 65
  6. 35
  7. 56
  8. 25
  9. Yes
  10. 114
  11. 30
  12. 104
  13. 90
  14. 67
  15. 63
  16. 17
  17. 33
  18. 62
  19. 54
  20. 68
  21. 27
  22. 60
  23. 77
  24. 74
  25. 13
  26. 37
  27. 27
  28. 33
  29. 134
  30. 90
  31. 53
  32. 24
  33. 97
  34. 77
  35. 50
  36. 144
  37. No
  38. 71
  39. 12
  40. No

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