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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 14 · 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 two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  2. 2.In triangle ABC, angle A = 38° and angle B = 54°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 60° and angle B = 37°. What is angle C (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  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 triangle ABC, angle A = 51° and angle B = 83°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 5 cm, 7 cm and 7 cm? (a) Yes (b) No
  10. 10.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  12. 12.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  13. 13.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 2 cm, 8 cm and 8 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 19 cm, 10 cm and 7 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 12 cm, 23 cm and 10 cm? (a) No (b) Yes
  17. 17.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 91° and angle B = 63°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 72° and 67°. What is the exterior angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 58° and 74°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 20 cm, 8 cm and 8 cm? (a) Yes (b) No
  27. 27.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 29° and 80°. What is the exterior angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 42° and 64°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 10 cm and 5 cm? (a) No (b) Yes
  33. 33.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 45° and 75°. What is the exterior angle (in degrees)?
  35. 35.Can a triangle have sides of 8 cm, 1 cm and 8 cm? (a) No (b) Yes
  36. 36.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 9 cm and 19 cm? (a) Yes (b) No
  38. 38.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 17
  2. 88
  3. 98
  4. 83
  5. 20
  6. 53
  7. 54
  8. 46
  9. Yes
  10. 17
  11. 48
  12. 10
  13. 42
  14. Yes
  15. No
  16. No
  17. 65
  18. 26
  19. 72
  20. 139
  21. 132
  22. 52
  23. 90
  24. 84
  25. 20
  26. No
  27. 75
  28. 109
  29. 106
  30. 79
  31. 14
  32. Yes
  33. 100
  34. 120
  35. Yes
  36. 67
  37. Yes
  38. 25
  39. 45
  40. 100

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