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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 750 · 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 an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 3 cm, 5 cm and 4 cm? (a) Yes (b) No
  3. 3.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  4. 4.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 60° and 58°. What is the exterior angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 90° and angle B = 60°. What is angle C (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  11. 11.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  13. 13.Can a triangle have sides of 9 cm, 7 cm and 19 cm? (a) No (b) Yes
  14. 14.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 64° and angle B = 80°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  19. 19.Can a triangle have sides of 13 cm, 6 cm and 4 cm? (a) Yes (b) No
  20. 20.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 80° and 43°. What is the exterior angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 25° and 58°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  25. 25.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)?
  26. 26.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  29. 29.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  30. 30.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  31. 31.Can a triangle have sides of 22 cm, 10 cm and 11 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 10 cm, 25 cm and 11 cm? (a) No (b) Yes
  33. 33.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  34. 34.In triangle ABC, angle A = 38° and angle B = 113°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 28° and 47°. What is the exterior angle (in degrees)?
  36. 36.In triangle ABC, angle A = 32° and angle B = 62°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 27° and 24°. What is the exterior angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 75° and 37°. What is the exterior angle (in degrees)?

Answer key

  1. 14
  2. Yes
  3. 15
  4. 90
  5. 26
  6. 118
  7. 52
  8. 45
  9. 30
  10. 25
  11. 118
  12. 5
  13. No
  14. 47
  15. 36
  16. 80
  17. 120
  18. 71
  19. No
  20. 20
  21. 36
  22. 123
  23. 83
  24. 45
  25. 7
  26. 71
  27. 52
  28. 90
  29. 29
  30. 33
  31. No
  32. No
  33. 15
  34. 29
  35. 75
  36. 86
  37. 56
  38. 51
  39. 28
  40. 112

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