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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 168 · 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 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  2. 2.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 41° and angle B = 97°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 100° and angle B = 34°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 3 cm and 5 cm? (a) Yes (b) No
  10. 10.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.Can a triangle have sides of 3 cm, 6 cm and 5 cm? (a) No (b) Yes
  17. 17.In triangle ABC, angle A = 23° and angle B = 41°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  19. 19.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)?
  20. 20.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 40° and angle B = 110°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 71° and angle B = 21°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 53° and angle B = 22°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 30° and angle B = 46°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 76° and angle B = 38°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 73° and 30°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 70° and angle B = 67°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 6 cm and 16 cm? (a) Yes (b) No
  31. 31.The two interior opposite angles of a triangle are 49° and 20°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 11 cm, 3 cm and 4 cm? (a) Yes (b) No
  35. 35.Can a triangle have sides of 8 cm, 8 cm and 6 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  38. 38.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  40. 40.Can a triangle have sides of 11 cm, 4 cm and 10 cm? (a) No (b) Yes

Answer key

  1. 15
  2. 75
  3. 54
  4. 80
  5. 42
  6. 46
  7. 14
  8. 100
  9. No
  10. 26
  11. 140
  12. 138
  13. 12
  14. 45
  15. 90
  16. Yes
  17. 116
  18. 17
  19. 6
  20. 46
  21. 30
  22. 88
  23. 105
  24. 55
  25. 104
  26. 66
  27. 103
  28. 43
  29. 29
  30. No
  31. 69
  32. 100
  33. 16
  34. No
  35. Yes
  36. 58
  37. 4
  38. 36
  39. 10
  40. Yes

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