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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 396 · 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 angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  3. 3.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)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 63° and angle B = 54°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 53° and angle B = 30°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 26° and angle B = 107°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 61° and angle B = 29°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 47° and 37°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 4 cm, 17 cm and 11 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 4 cm, 1 cm and 4 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 65° and angle B = 87°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 4 cm, 9 cm and 9 cm? (a) No (b) Yes
  21. 21.In triangle ABC, angle A = 54° and angle B = 27°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 100° and angle B = 56°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 14 cm and 8 cm? (a) No (b) Yes
  28. 28.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  29. 29.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)?
  30. 30.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 56° and 22°. What is the exterior angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 59° and 44°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 14 cm, 12 cm and 7 cm? (a) No (b) Yes
  35. 35.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  36. 36.In triangle ABC, angle A = 48° and angle B = 35°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 13 cm, 9 cm and 9 cm? (a) No (b) Yes
  38. 38.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 70° and angle B = 44°. What is angle C (in degrees)?

Answer key

  1. 90
  2. 30
  3. 8
  4. 59
  5. 63
  6. 33
  7. 30
  8. 65
  9. 97
  10. 47
  11. 72
  12. 90
  13. 84
  14. No
  15. Yes
  16. 28
  17. 66
  18. 46
  19. 61
  20. Yes
  21. 99
  22. 50
  23. 17
  24. 24
  25. 11
  26. 79
  27. Yes
  28. 67
  29. 5
  30. 50
  31. 78
  32. 79
  33. 103
  34. Yes
  35. 24
  36. 97
  37. Yes
  38. 17
  39. 90
  40. 66

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