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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 99 · 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 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)?
  2. 2.In triangle ABC, angle A = 59° and angle B = 27°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 106°. 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 59° and 76°. What is the exterior angle (in degrees)?
  5. 5.Can a triangle have sides of 4 cm, 3 cm and 4 cm? (a) Yes (b) No
  6. 6.In triangle ABC, angle A = 22° and angle B = 117°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  9. 9.Can a triangle have sides of 10 cm, 16 cm and 6 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 6 cm, 7 cm and 4 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 56° and angle B = 32°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 55° and angle B = 78°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  17. 17.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)?
  18. 18.Can a triangle have sides of 8 cm, 3 cm and 10 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  20. 20.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)?
  21. 21.In triangle ABC, angle A = 67° and angle B = 47°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 27° and 78°. What is the exterior angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 51° and angle B = 64°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 26 cm, 12 cm and 10 cm? (a) Yes (b) No
  29. 29.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 21° and angle B = 112°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 48° and angle B = 37°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 24° and angle B = 119°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 62° and angle B = 90°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 95° and angle B = 30°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 37° and angle B = 121°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 86° and angle B = 58°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 29° and angle B = 85°. What is angle C (in degrees)?

Answer key

  1. 8
  2. 94
  3. 71
  4. 135
  5. Yes
  6. 41
  7. 45
  8. 17
  9. No
  10. 60
  11. Yes
  12. 92
  13. 30
  14. 47
  15. 71
  16. 100
  17. 6
  18. Yes
  19. 61
  20. 15
  21. 66
  22. 15
  23. 23
  24. 105
  25. 5
  26. 72
  27. 65
  28. No
  29. 30
  30. 47
  31. 95
  32. 37
  33. 77
  34. 28
  35. 55
  36. 41
  37. 77
  38. 22
  39. 36
  40. 66

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