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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 695 · 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.The two interior opposite angles of a triangle are 28° and 33°. What is the exterior angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  4. 4.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 15 cm, 4 cm and 12 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 49° and angle B = 49°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 5 cm, 5 cm and 10 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  11. 11.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 79° and angle B = 72°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 89° and angle B = 39°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  17. 17.Can a triangle have sides of 5 cm, 9 cm and 2 cm? (a) Yes (b) No
  18. 18.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  20. 20.Can a triangle have sides of 7 cm, 7 cm and 14 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 3 cm, 8 cm and 10 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 39° and 66°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 69° each. 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.Can a triangle have sides of 12 cm, 11 cm and 10 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 20 cm, 8 cm and 7 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 37° and angle B = 43°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 7 cm and 7 cm? (a) No (b) Yes

Answer key

  1. 61
  2. 25
  3. 47
  4. 48
  5. Yes
  6. 82
  7. 34
  8. No
  9. 40
  10. 7
  11. 100
  12. 39
  13. 29
  14. 52
  15. 26
  16. 84
  17. No
  18. 64
  19. 39
  20. No
  21. 16
  22. 20
  23. 70
  24. Yes
  25. 49
  26. 48
  27. 105
  28. 72
  29. 75
  30. 42
  31. 24
  32. Yes
  33. 62
  34. 63
  35. 71
  36. 67
  37. No
  38. 65
  39. 100
  40. Yes

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