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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 915 · 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 = 22° and angle B = 34°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 76° and 54°. What is the exterior angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 33° and 43°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 43° and 51°. What is the exterior angle (in degrees)?
  5. 5.Can a triangle have sides of 10 cm, 18 cm and 8 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 74° and angle B = 40°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 23° and angle B = 120°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 5 cm and 18 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 43° and angle B = 69°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  22. 22.In triangle ABC, angle A = 37° and angle B = 95°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 17 cm, 7 cm and 7 cm? (a) No (b) Yes
  24. 24.Can a triangle have sides of 9 cm, 7 cm and 9 cm? (a) No (b) Yes
  25. 25.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 10 cm and 27 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 18 cm, 5 cm and 12 cm? (a) Yes (b) No
  30. 30.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  31. 31.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  32. 32.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  35. 35.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 7 cm, 2 cm and 4 cm? (a) Yes (b) No
  37. 37.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 9 cm and 6 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 9 cm, 9 cm and 2 cm? (a) No (b) Yes
  40. 40.The two interior opposite angles of a triangle are 34° and 74°. What is the exterior angle (in degrees)?

Answer key

  1. 124
  2. 130
  3. 76
  4. 94
  5. No
  6. 106
  7. 66
  8. 37
  9. 102
  10. 45
  11. 24
  12. 32
  13. 12
  14. 84
  15. No
  16. 68
  17. 58
  18. 30
  19. 25
  20. 54
  21. 61
  22. 48
  23. No
  24. Yes
  25. 17
  26. 23
  27. 40
  28. No
  29. No
  30. 17
  31. 25
  32. 69
  33. 140
  34. 30
  35. 30
  36. No
  37. 100
  38. Yes
  39. Yes
  40. 108

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