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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 667 · 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 longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 19 cm, 9 cm and 7 cm? (a) Yes (b) No
  4. 4.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 45° and 40°. What is the exterior angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 50° and 22°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 30° and 60°. What is the exterior angle (in degrees)?
  10. 10.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 4 cm, 14 cm and 6 cm? (a) Yes (b) No
  12. 12.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  13. 13.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 79° and angle B = 67°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 20° and angle B = 79°. What is angle C (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  20. 20.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  21. 21.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 12 cm, 9 cm and 6 cm? (a) Yes (b) No
  24. 24.The two interior opposite angles of a triangle are 40° and 41°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 30° and angle B = 79°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 95° and angle B = 31°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 8 cm, 14 cm and 9 cm? (a) Yes (b) No
  30. 30.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)?
  31. 31.In triangle ABC, angle A = 77° and angle B = 38°. What is angle C (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.Can a triangle have sides of 19 cm, 10 cm and 12 cm? (a) No (b) Yes
  34. 34.The two interior opposite angles of a triangle are 64° and 30°. What is the exterior angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?

Answer key

  1. 6
  2. 63
  3. No
  4. 13
  5. 85
  6. 72
  7. 56
  8. 15
  9. 90
  10. 75
  11. No
  12. 12
  13. 28
  14. 75
  15. 34
  16. 90
  17. 80
  18. 81
  19. 26
  20. 26
  21. 34
  22. 42
  23. Yes
  24. 81
  25. 71
  26. 54
  27. 20
  28. 51
  29. Yes
  30. 24
  31. 65
  32. 3
  33. Yes
  34. 94
  35. 90
  36. 72
  37. 16
  38. 40
  39. 134
  40. 24

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