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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 239 · 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 = 97° and angle B = 27°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  3. 3.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 73° and 29°. What is the exterior angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 24° and angle B = 127°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 9 cm, 11 cm and 9 cm? (a) Yes (b) No
  9. 9.In triangle ABC, angle A = 75° and angle B = 76°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 10 cm, 5 cm and 11 cm? (a) No (b) Yes
  11. 11.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 75° and angle B = 68°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 74° and 38°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 7 cm, 17 cm and 10 cm? (a) No (b) Yes
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  19. 19.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  23. 23.In triangle ABC, angle A = 69° and angle B = 52°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 91° and angle B = 64°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 22 cm, 12 cm and 9 cm? (a) No (b) Yes
  29. 29.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 95° and angle B = 41°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 29° and angle B = 114°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 55° and angle B = 41°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 8 cm, 2 cm and 4 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 11 cm, 21 cm and 10 cm? (a) Yes (b) No
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 56
  2. 67
  3. 44
  4. 102
  5. 25
  6. 29
  7. 60
  8. Yes
  9. 29
  10. Yes
  11. 62
  12. 37
  13. 61
  14. 112
  15. No
  16. 90
  17. 53
  18. 17
  19. 132
  20. 69
  21. 11
  22. 57
  23. 59
  24. 90
  25. 25
  26. 31
  27. 72
  28. No
  29. 61
  30. 71
  31. 106
  32. 44
  33. 12
  34. 25
  35. 37
  36. 84
  37. 40
  38. No
  39. No
  40. 36

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