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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 410 · 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.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 24° and 79°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 57° and angle B = 82°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 15 cm and 4 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 18 cm, 6 cm and 8 cm? (a) No (b) Yes
  13. 13.Can a triangle have sides of 10 cm, 5 cm and 9 cm? (a) Yes (b) No
  14. 14.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  17. 17.Can a triangle have sides of 12 cm, 9 cm and 21 cm? (a) No (b) Yes
  18. 18.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 79° and angle B = 34°. What is angle C (in degrees)?
  22. 22.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)?
  23. 23.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  25. 25.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)?
  26. 26.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 68° and 58°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 4 cm, 11 cm and 19 cm? (a) Yes (b) No
  29. 29.In triangle ABC, angle A = 52° and angle B = 101°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 99° and angle B = 45°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 21° and 60°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 86° and angle B = 59°. What is angle C (in degrees)?
  40. 40.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)?

Answer key

  1. 34
  2. 103
  3. 66
  4. 41
  5. 96
  6. 47
  7. 44
  8. 51
  9. 30
  10. 77
  11. No
  12. No
  13. Yes
  14. 23
  15. 39
  16. 50
  17. No
  18. 72
  19. 72
  20. 17
  21. 67
  22. 15
  23. 50
  24. 30
  25. 24
  26. 30
  27. 126
  28. No
  29. 27
  30. 102
  31. 36
  32. 90
  33. 100
  34. 20
  35. 73
  36. 60
  37. 138
  38. 81
  39. 35
  40. 8

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