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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 361 · 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 angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  9. 9.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  10. 10.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 71°. What is the other one (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.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 49° and 70°. What is the exterior angle (in degrees)?
  17. 17.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)?
  18. 18.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 25 cm and 11 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  23. 23.Can a triangle have sides of 10 cm, 10 cm and 8 cm? (a) No (b) Yes
  24. 24.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 74° and 64°. What is the exterior angle (in degrees)?
  27. 27.Can a triangle have sides of 12 cm, 10 cm and 7 cm? (a) No (b) Yes
  28. 28.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 59° and angle B = 41°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 33° and 51°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 35° and angle B = 46°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 61° and angle B = 28°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  36. 36.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)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  38. 38.In triangle ABC, angle A = 85° and angle B = 68°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?

Answer key

  1. 36
  2. 80
  3. 38
  4. 25
  5. 19
  6. 50
  7. 36
  8. 39
  9. 20
  10. 138
  11. 72
  12. 41
  13. 17
  14. 46
  15. 90
  16. 119
  17. 12
  18. 26
  19. 14
  20. 69
  21. No
  22. 120
  23. Yes
  24. 110
  25. 59
  26. 138
  27. Yes
  28. 84
  29. 61
  30. 80
  31. 54
  32. 84
  33. 99
  34. 91
  35. 41
  36. 18
  37. 77
  38. 27
  39. 36
  40. 34

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