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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 765 · 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.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 11 cm and 21 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 50° and angle B = 27°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 70° and 28°. What is the exterior angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  8. 8.In triangle ABC, angle A = 37° and angle B = 52°. What is angle C (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.In triangle ABC, angle A = 87° and angle B = 40°. What is angle C (in degrees)?
  11. 11.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)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 37° and angle B = 73°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 42° and angle B = 50°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 73° and 75°. What is the exterior angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 61° and 27°. What is the exterior angle (in degrees)?
  21. 21.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 66° and 36°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 39° and angle B = 54°. What is angle C (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 triangle ABC, angle A = 76° and angle B = 43°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 44°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 52° and angle B = 106°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  34. 34.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.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)?
  36. 36.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 52° and angle B = 41°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  40. 40.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?

Answer key

  1. 49
  2. No
  3. 103
  4. 70
  5. 98
  6. 72
  7. 73
  8. 91
  9. 10
  10. 53
  11. 8
  12. 16
  13. 70
  14. 40
  15. 88
  16. 54
  17. 148
  18. 36
  19. 67
  20. 88
  21. 25
  22. 55
  23. 102
  24. 87
  25. 7
  26. 61
  27. 23
  28. 40
  29. 22
  30. 108
  31. 12
  32. 27
  33. 5
  34. 20
  35. 24
  36. 11
  37. 87
  38. 80
  39. 36
  40. 75

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