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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 608 · 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 124°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  2. 2.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)?
  3. 3.In triangle ABC, angle A = 25° and angle B = 113°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 38° and 42°. What is the exterior angle (in degrees)?
  5. 5.In triangle ABC, angle A = 59° and angle B = 44°. What is angle C (in degrees)?
  6. 6.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  7. 7.Can a triangle have sides of 5 cm, 4 cm and 4 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 63° and angle B = 84°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  14. 14.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 46° and angle B = 40°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  20. 20.Can a triangle have sides of 15 cm, 4 cm and 7 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 11 cm, 22 cm and 8 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 33° and angle B = 111°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 22° and 62°. What is the exterior angle (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 7 cm and 12 cm? (a) No (b) Yes
  28. 28.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 28° and 61°. What is the exterior angle (in degrees)?
  31. 31.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 45° and 75°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 33° and angle B = 63°. What is angle C (in degrees)?
  34. 34.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  35. 35.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  36. 36.Can a triangle have sides of 5 cm, 8 cm and 2 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 8 cm, 13 cm and 8 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  40. 40.Can a triangle have sides of 8 cm, 13 cm and 3 cm? (a) Yes (b) No

Answer key

  1. 77
  2. 8
  3. 42
  4. 80
  5. 77
  6. 7
  7. Yes
  8. 124
  9. 50
  10. 13
  11. 120
  12. 33
  13. 25
  14. 72
  15. 118
  16. 94
  17. 70
  18. 84
  19. 20
  20. No
  21. No
  22. 72
  23. 23
  24. 36
  25. 52
  26. 84
  27. Yes
  28. 23
  29. 14
  30. 89
  31. 45
  32. 120
  33. 84
  34. 6
  35. 45
  36. No
  37. Yes
  38. 57
  39. 12
  40. No

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