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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 656 · 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 8 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 61° and 21°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 26° and angle B = 44°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 90° and angle B = 44°. What is angle C (in degrees)?
  10. 10.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  11. 11.Can a triangle have sides of 9 cm, 7 cm and 5 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 20° and angle B = 23°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 71° and 51°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 8 cm and 10 cm? (a) No (b) Yes
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  20. 20.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 11 cm, 5 cm and 20 cm? (a) No (b) Yes
  26. 26.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.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)?
  29. 29.Can a triangle have sides of 6 cm, 8 cm and 8 cm? (a) Yes (b) No
  30. 30.The two interior opposite angles of a triangle are 25° and 41°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 5 cm and 6 cm? (a) No (b) Yes
  32. 32.Can a triangle have sides of 2 cm, 5 cm and 5 cm? (a) No (b) Yes
  33. 33.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 54° and 44°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 97° and angle B = 47°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 24° and 36°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 20° and 21°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 92° and angle B = 33°. What is angle C (in degrees)?
  40. 40.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?

Answer key

  1. 17
  2. 45
  3. 82
  4. 110
  5. 31
  6. 27
  7. 21
  8. 36
  9. 46
  10. 10
  11. Yes
  12. 137
  13. 100
  14. 122
  15. Yes
  16. 90
  17. 39
  18. 63
  19. 66
  20. 78
  21. 72
  22. 74
  23. 90
  24. 61
  25. No
  26. 13
  27. 90
  28. 8
  29. Yes
  30. 66
  31. Yes
  32. Yes
  33. 46
  34. 98
  35. 36
  36. 60
  37. 110
  38. 41
  39. 55
  40. 16

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