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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 119 · 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.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 28° and 46°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  5. 5.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  9. 9.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 62° and angle B = 97°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 11 cm, 4 cm and 11 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 10 cm, 12 cm and 16 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 86° and angle B = 33°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 62° and angle B = 72°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 28° and angle B = 115°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 65° and 34°. What is the exterior angle (in degrees)?
  22. 22.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  25. 25.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 93° and angle B = 63°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 71° and angle B = 37°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 87° and angle B = 20°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  36. 36.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)?
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.Can a triangle have sides of 8 cm, 9 cm and 6 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 63° and angle B = 26°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 12 cm, 12 cm and 8 cm? (a) Yes (b) No

Answer key

  1. 79
  2. 74
  3. 58
  4. 25
  5. 23
  6. 72
  7. 40
  8. 17
  9. 29
  10. 25
  11. 64
  12. 21
  13. Yes
  14. 15
  15. Yes
  16. 61
  17. 73
  18. 46
  19. 73
  20. 37
  21. 99
  22. 28
  23. 94
  24. 3
  25. 72
  26. 54
  27. 90
  28. 24
  29. 72
  30. 18
  31. 4
  32. 73
  33. 84
  34. 90
  35. 100
  36. 8
  37. 17
  38. Yes
  39. 91
  40. Yes

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