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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 355 · 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 57° and 78°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 73° and 22°. What is the exterior angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 79° and angle B = 33°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 28° and angle B = 42°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 12 cm, 10 cm and 14 cm? (a) Yes (b) No
  9. 9.In triangle ABC, angle A = 73° and angle B = 76°. What is angle C (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.The two interior opposite angles of a triangle are 72° and 75°. What is the exterior angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 57° and angle B = 47°. What is angle C (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  18. 18.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)?
  19. 19.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 25° and 41°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  23. 23.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  28. 28.Can a triangle have sides of 11 cm, 8 cm and 23 cm? (a) Yes (b) No
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  31. 31.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)?
  32. 32.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  35. 35.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 9 cm and 19 cm? (a) Yes (b) No
  38. 38.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 35° and 48°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 22 cm, 8 cm and 12 cm? (a) No (b) Yes

Answer key

  1. 135
  2. 26
  3. 95
  4. 54
  5. 64
  6. 68
  7. 110
  8. Yes
  9. 31
  10. 70
  11. 147
  12. 5
  13. 32
  14. 73
  15. 76
  16. 25
  17. 57
  18. 15
  19. 60
  20. 66
  21. 69
  22. 21
  23. 80
  24. 90
  25. 88
  26. 17
  27. 26
  28. No
  29. 40
  30. 58
  31. 7
  32. 90
  33. 36
  34. 65
  35. 6
  36. 71
  37. No
  38. 55
  39. 83
  40. No

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