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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 425 · 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 = 47° and angle B = 72°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 86° and angle B = 27°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 79° and angle B = 74°. What is angle C (in degrees)?
  4. 4.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  5. 5.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 5 cm and 18 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 12 cm, 8 cm and 21 cm? (a) Yes (b) No
  9. 9.In triangle ABC, angle A = 31° and angle B = 118°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  11. 11.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 29° and 53°. What is the exterior angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 62° and 74°. What is the exterior angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 96° and angle B = 29°. What is angle C (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 75° and angle B = 27°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 23 cm, 9 cm and 9 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 59° and angle B = 88°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  27. 27.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 16 cm and 6 cm? (a) No (b) Yes
  29. 29.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 50° and angle B = 106°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 4 cm, 10 cm and 2 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 31° and 25°. What is the exterior angle (in degrees)?

Answer key

  1. 61
  2. 67
  3. 27
  4. 8
  5. 34
  6. 63
  7. No
  8. No
  9. 31
  10. 34
  11. 22
  12. 22
  13. 34
  14. 25
  15. 67
  16. 82
  17. 136
  18. 66
  19. 27
  20. 55
  21. 17
  22. 90
  23. 78
  24. No
  25. 33
  26. 20
  27. 44
  28. No
  29. 90
  30. 24
  31. 68
  32. No
  33. No
  34. 65
  35. 20
  36. 39
  37. 90
  38. 70
  39. 51
  40. 56

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