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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 921 · 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.In triangle ABC, angle A = 29° and angle B = 97°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 59° and 45°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 38° and 59°. What is the exterior angle (in degrees)?
  9. 9.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)?
  10. 10.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 13 cm, 8 cm and 4 cm? (a) No (b) Yes
  16. 16.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  17. 17.Can a triangle have sides of 10 cm, 8 cm and 23 cm? (a) No (b) Yes
  18. 18.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 50° and angle B = 60°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 81° and angle B = 62°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  24. 24.In triangle ABC, angle A = 87° and angle B = 31°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 6 cm, 8 cm and 8 cm? (a) No (b) Yes
  26. 26.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  28. 28.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  29. 29.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 2 cm and 6 cm? (a) No (b) Yes
  32. 32.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.Can a triangle have sides of 1 cm, 4 cm and 4 cm? (a) No (b) Yes
  35. 35.Can a triangle have sides of 10 cm, 12 cm and 26 cm? (a) Yes (b) No
  36. 36.In a right-angled triangle, one of the other two angles is 17°. 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 two interior opposite angles of a triangle are 48° and 45°. What is the exterior angle (in degrees)?
  39. 39.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)?
  40. 40.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?

Answer key

  1. 54
  2. 104
  3. 26
  4. 50
  5. 18
  6. 52
  7. 72
  8. 97
  9. 7
  10. 40
  11. 32
  12. 14
  13. 68
  14. 80
  15. No
  16. 54
  17. No
  18. 72
  19. 58
  20. 70
  21. 118
  22. 37
  23. 44
  24. 62
  25. Yes
  26. 74
  27. 39
  28. 39
  29. 60
  30. 77
  31. No
  32. 75
  33. 17
  34. Yes
  35. No
  36. 73
  37. 24
  38. 93
  39. 4
  40. 61

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