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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 156 · 40 sums
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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 8 cm and 6 cm. How long is the longest side (in cm)?
  2. 2.Can a triangle have sides of 7 cm, 9 cm and 16 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 52° and angle B = 32°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 56° and angle B = 76°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  10. 10.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 24 cm, 10 cm and 10 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  23. 23.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 52° and angle B = 79°. What is angle C (in degrees)?
  27. 27.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)?
  28. 28.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)?
  29. 29.In triangle ABC, angle A = 49° and angle B = 70°. What is angle C (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  31. 31.Can a triangle have sides of 9 cm, 6 cm and 6 cm? (a) No (b) Yes
  32. 32.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  33. 33.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  37. 37.In triangle ABC, angle A = 48° and angle B = 48°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 66° and 49°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 72° and angle B = 38°. What is angle C (in degrees)?

Answer key

  1. 10
  2. No
  3. 100
  4. 96
  5. 72
  6. 11
  7. 29
  8. 48
  9. 44
  10. 27
  11. 25
  12. 44
  13. No
  14. 28
  15. 100
  16. 23
  17. 64
  18. 36
  19. 84
  20. 23
  21. 17
  22. 73
  23. 63
  24. 20
  25. 70
  26. 49
  27. 8
  28. 15
  29. 61
  30. 25
  31. Yes
  32. 84
  33. 43
  34. 126
  35. 15
  36. 13
  37. 84
  38. 25
  39. 115
  40. 70

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