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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 289 · 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 two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  7. 7.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 77° and 37°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 10 cm, 2 cm and 11 cm? (a) Yes (b) No
  10. 10.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 70° and 32°. What is the exterior angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 6 cm, 13 cm and 5 cm? (a) No (b) Yes
  14. 14.In triangle ABC, angle A = 27° and angle B = 103°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 25 cm, 12 cm and 8 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 60° and angle B = 72°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 49° and angle B = 23°. What is angle C (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  21. 21.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 77° and angle B = 78°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 16 cm, 5 cm and 11 cm? (a) Yes (b) No
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 5 cm, 8 cm and 7 cm? (a) No (b) Yes
  28. 28.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  29. 29.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 95° and angle B = 43°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 20 cm and 7 cm? (a) Yes (b) No
  33. 33.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 4 cm and 10 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 40° and angle B = 27°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  38. 38.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?

Answer key

  1. 17
  2. 90
  3. 5
  4. 32
  5. 18
  6. 25
  7. 76
  8. 114
  9. Yes
  10. 63
  11. 102
  12. 42
  13. No
  14. 50
  15. No
  16. 48
  17. 80
  18. 108
  19. 17
  20. 36
  21. 59
  22. 25
  23. No
  24. 72
  25. 12
  26. 53
  27. Yes
  28. 20
  29. 65
  30. 90
  31. 42
  32. No
  33. 43
  34. Yes
  35. 113
  36. 47
  37. 24
  38. 84
  39. 72
  40. 58

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