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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 593 · 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 two interior opposite angles of a triangle are 43° and 38°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  7. 7.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  8. 8.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)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  11. 11.In triangle ABC, angle A = 72° and angle B = 69°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 29° and 54°. What is the exterior angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 61° and angle B = 80°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 100° and angle B = 29°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 83° and angle B = 60°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (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 11°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 25° and 63°. What is the exterior angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 64° and 61°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 53° and angle B = 47°. What is angle C (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 56° and 37°. What is the exterior angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 11 cm, 9 cm and 2 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 91° and angle B = 35°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 38° and angle B = 96°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  34. 34.Can a triangle have sides of 5 cm, 7 cm and 5 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  36. 36.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)?
  37. 37.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  38. 38.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  40. 40.Can a triangle have sides of 18 cm, 10 cm and 8 cm? (a) Yes (b) No

Answer key

  1. 81
  2. 49
  3. 65
  4. 48
  5. 43
  6. 12
  7. 106
  8. 15
  9. 30
  10. 15
  11. 39
  12. 42
  13. 83
  14. 70
  15. 39
  16. 51
  17. 37
  18. 67
  19. 6
  20. 79
  21. 90
  22. 88
  23. 125
  24. 80
  25. 93
  26. 41
  27. No
  28. 73
  29. 54
  30. 46
  31. 20
  32. 10
  33. 55
  34. Yes
  35. 66
  36. 24
  37. 12
  38. 71
  39. 25
  40. No

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