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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 856 · 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 angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 80° and 34°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 12 cm and 4 cm? (a) No (b) Yes
  5. 5.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)?
  6. 6.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  7. 7.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 39° and angle B = 44°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 8 cm, 3 cm and 15 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 66° and angle B = 69°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 61° and 63°. What is the exterior angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 21° and 37°. What is the exterior angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  17. 17.Can a triangle have sides of 8 cm, 3 cm and 3 cm? (a) No (b) Yes
  18. 18.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 34° and 40°. What is the exterior angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 29° and 34°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 22° and angle B = 123°. What is angle C (in degrees)?
  24. 24.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)?
  25. 25.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) No (b) Yes
  26. 26.Can a triangle have sides of 9 cm, 10 cm and 6 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  28. 28.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)?
  29. 29.Can a triangle have sides of 12 cm, 8 cm and 23 cm? (a) Yes (b) No
  30. 30.Can a triangle have sides of 13 cm, 12 cm and 2 cm? (a) Yes (b) No
  31. 31.The two interior opposite angles of a triangle are 65° and 25°. What is the exterior angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.Can a triangle have sides of 14 cm, 7 cm and 7 cm? (a) Yes (b) No
  36. 36.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 92° and angle B = 41°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 89° and angle B = 34°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 22° and angle B = 48°. What is angle C (in degrees)?

Answer key

  1. 72
  2. 114
  3. 60
  4. Yes
  5. 8
  6. 17
  7. 60
  8. 17
  9. 97
  10. No
  11. 45
  12. 52
  13. 42
  14. 124
  15. 58
  16. 30
  17. No
  18. 100
  19. 35
  20. 18
  21. 74
  22. 63
  23. 35
  24. 12
  25. No
  26. Yes
  27. 26
  28. 16
  29. No
  30. Yes
  31. 90
  32. 3
  33. 108
  34. 20
  35. No
  36. 62
  37. 47
  38. 57
  39. 51
  40. 110

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