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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 231 · 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 = 74° and angle B = 33°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 33° and angle B = 59°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 55° and angle B = 39°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 25 cm, 11 cm and 9 cm? (a) Yes (b) No
  12. 12.The two interior opposite angles of a triangle are 66° and 58°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 37° and angle B = 81°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 10 cm, 11 cm and 10 cm? (a) Yes (b) No
  16. 16.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 37° and angle B = 49°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 14 cm and 4 cm? (a) Yes (b) No
  21. 21.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 7 cm, 13 cm and 4 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 36° and angle B = 96°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  29. 29.Can a triangle have sides of 13 cm, 11 cm and 5 cm? (a) Yes (b) No
  30. 30.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  35. 35.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)?
  36. 36.The two interior opposite angles of a triangle are 52° and 50°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 19 cm and 6 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 73
  2. 35
  3. 20
  4. 21
  5. 71
  6. 20
  7. 88
  8. 76
  9. 74
  10. 86
  11. No
  12. 124
  13. 72
  14. 62
  15. Yes
  16. 40
  17. 30
  18. 78
  19. 94
  20. No
  21. 25
  22. 122
  23. 42
  24. 37
  25. No
  26. 51
  27. 48
  28. 20
  29. Yes
  30. 69
  31. 32
  32. 90
  33. 134
  34. 17
  35. 5
  36. 102
  37. No
  38. 22
  39. 60
  40. 100

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