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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 169 · 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 an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  4. 4.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  6. 6.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)?
  7. 7.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 25° and angle B = 95°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 20° and 58°. What is the exterior angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  13. 13.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)?
  14. 14.In triangle ABC, angle A = 69° and angle B = 41°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 88° and angle B = 57°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 5 cm and 11 cm? (a) Yes (b) No
  17. 17.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 12 cm and 13 cm? (a) No (b) Yes
  21. 21.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 16 cm, 4 cm and 12 cm? (a) No (b) Yes
  23. 23.Can a triangle have sides of 11 cm, 24 cm and 8 cm? (a) Yes (b) No
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  25. 25.Can a triangle have sides of 11 cm, 9 cm and 24 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 51° and angle B = 34°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 72° and 46°. What is the exterior angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 4 cm, 3 cm and 7 cm? (a) No (b) Yes
  31. 31.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 43° and angle B = 27°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 39° and 51°. What is the exterior angle (in degrees)?
  36. 36.In triangle ABC, angle A = 41° and angle B = 65°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 24° and 45°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?

Answer key

  1. 47
  2. 72
  3. 25
  4. 52
  5. 114
  6. 24
  7. 22
  8. 35
  9. 60
  10. 27
  11. 78
  12. 40
  13. 8
  14. 70
  15. 35
  16. Yes
  17. 106
  18. 72
  19. 80
  20. Yes
  21. 15
  22. No
  23. No
  24. 25
  25. No
  26. 95
  27. 118
  28. 22
  29. 77
  30. No
  31. 24
  32. 110
  33. 61
  34. 90
  35. 90
  36. 74
  37. 39
  38. 69
  39. 72
  40. 20

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