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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 372 · 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 140°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 71° and 68°. What is the exterior angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 21 cm, 10 cm and 10 cm? (a) No (b) Yes
  7. 7.Can a triangle have sides of 18 cm, 9 cm and 8 cm? (a) No (b) Yes
  8. 8.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)?
  9. 9.Can a triangle have sides of 4 cm, 5 cm and 5 cm? (a) Yes (b) No
  10. 10.Can a triangle have sides of 10 cm, 7 cm and 21 cm? (a) No (b) Yes
  11. 11.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 56° and angle B = 29°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 32° and angle B = 22°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 97° and angle B = 27°. What is angle C (in degrees)?
  15. 15.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)?
  16. 16.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  17. 17.Can a triangle have sides of 19 cm, 9 cm and 7 cm? (a) No (b) Yes
  18. 18.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 81° and angle B = 75°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 57° and angle B = 99°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 18 cm, 7 cm and 10 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  28. 28.An exterior angle of a triangle is 150°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  29. 29.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  30. 30.Can a triangle have sides of 4 cm, 4 cm and 10 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 3 cm, 11 cm and 3 cm? (a) No (b) Yes
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 98° and angle B = 47°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 10 cm and 5 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  39. 39.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?

Answer key

  1. 70
  2. 139
  3. 39
  4. 29
  5. 128
  6. No
  7. No
  8. 8
  9. Yes
  10. No
  11. 30
  12. 95
  13. 126
  14. 56
  15. 24
  16. 21
  17. No
  18. 38
  19. 75
  20. 90
  21. 90
  22. 114
  23. 24
  24. 24
  25. No
  26. 120
  27. 36
  28. 74
  29. 8
  30. No
  31. No
  32. 16
  33. 20
  34. 35
  35. Yes
  36. 48
  37. 58
  38. 15
  39. 67
  40. 52

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