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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 712 · 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 5 : 6 : 7. What is the biggest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 9 cm, 13 cm and 9 cm? (a) Yes (b) No
  4. 4.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)?
  5. 5.In triangle ABC, angle A = 90° and angle B = 33°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 5 cm, 7 cm and 3 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 60° and angle B = 97°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 5 cm, 12 cm and 7 cm? (a) No (b) Yes
  13. 13.Can a triangle have sides of 8 cm, 11 cm and 7 cm? (a) Yes (b) No
  14. 14.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)?
  15. 15.The two interior opposite angles of a triangle are 30° and 66°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 24 cm, 10 cm and 10 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 45° and angle B = 59°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 85° and angle B = 40°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 56° and 80°. What is the exterior angle (in degrees)?
  21. 21.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  24. 24.The two interior opposite angles of a triangle are 56° and 28°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 40° and angle B = 70°. What is angle C (in degrees)?
  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.Can a triangle have sides of 4 cm, 6 cm and 2 cm? (a) Yes (b) No
  28. 28.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  29. 29.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 40° and angle B = 31°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 32° and 60°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 71° and 38°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 8 cm, 17 cm and 7 cm? (a) Yes (b) No

Answer key

  1. 70
  2. 80
  3. Yes
  4. 8
  5. 57
  6. Yes
  7. 54
  8. 34
  9. 136
  10. 23
  11. 112
  12. No
  13. Yes
  14. 16
  15. 96
  16. No
  17. 76
  18. 55
  19. 49
  20. 136
  21. 57
  22. 50
  23. 17
  24. 84
  25. 70
  26. 13
  27. No
  28. 18
  29. 75
  30. 73
  31. 20
  32. 8
  33. 40
  34. 109
  35. 80
  36. 19
  37. 92
  38. 45
  39. 109
  40. No

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