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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 208 · 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 = 23° and angle B = 27°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 41° and 38°. What is the exterior angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 46° and 27°. What is the exterior angle (in degrees)?
  6. 6.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)?
  7. 7.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  8. 8.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 7 cm, 3 cm and 7 cm? (a) No (b) Yes
  10. 10.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  12. 12.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)?
  13. 13.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 88° and angle B = 58°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 4 cm and 10 cm? (a) Yes (b) No
  16. 16.The two interior opposite angles of a triangle are 62° and 34°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  20. 20.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 21° and 20°. What is the exterior angle (in degrees)?
  22. 22.In triangle ABC, angle A = 30° and angle B = 118°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 93° and angle B = 56°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  26. 26.The two interior opposite angles of a triangle are 68° and 31°. What is the exterior angle (in degrees)?
  27. 27.Can a triangle have sides of 3 cm, 11 cm and 3 cm? (a) No (b) Yes
  28. 28.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 27° and 22°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  33. 33.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)?
  34. 34.In triangle ABC, angle A = 69° and angle B = 85°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 23° and angle B = 61°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 12 cm, 21 cm and 8 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 46° and 69°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  40. 40.In triangle ABC, angle A = 24° and angle B = 98°. What is angle C (in degrees)?

Answer key

  1. 130
  2. 15
  3. 114
  4. 79
  5. 73
  6. 15
  7. 3
  8. 104
  9. Yes
  10. 23
  11. 31
  12. 12
  13. 33
  14. 34
  15. Yes
  16. 96
  17. 132
  18. 122
  19. 10
  20. 90
  21. 41
  22. 32
  23. 39
  24. 31
  25. 26
  26. 99
  27. No
  28. 52
  29. 27
  30. 49
  31. 38
  32. 37
  33. 24
  34. 26
  35. 96
  36. No
  37. 115
  38. 62
  39. 10
  40. 58

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