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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 954 · 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 a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  2. 2.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)?
  3. 3.Can a triangle have sides of 3 cm, 6 cm and 11 cm? (a) Yes (b) No
  4. 4.Can a triangle have sides of 12 cm, 10 cm and 12 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 46° and 74°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 83° and angle B = 33°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 74° and angle B = 31°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  11. 11.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 73° and angle B = 59°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 41° and angle B = 64°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  28. 28.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  29. 29.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  31. 31.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)?
  32. 32.In triangle ABC, angle A = 67° and angle B = 66°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 30° and angle B = 62°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?

Answer key

  1. 79
  2. 15
  3. No
  4. Yes
  5. 120
  6. 64
  7. 25
  8. 75
  9. 29
  10. 20
  11. 33
  12. 48
  13. 17
  14. 57
  15. 124
  16. 32
  17. 72
  18. 60
  19. 57
  20. 37
  21. 39
  22. 45
  23. 75
  24. 75
  25. 33
  26. 73
  27. 18
  28. 16
  29. 54
  30. 68
  31. 24
  32. 47
  33. 10
  34. 20
  35. 56
  36. 29
  37. 36
  38. 25
  39. 88
  40. 5

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