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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 10 · 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 61° and 77°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 8 cm, 8 cm and 13 cm? (a) No (b) Yes
  3. 3.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 24° and 33°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 21° and 32°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 8 cm, 12 cm and 13 cm? (a) Yes (b) No
  10. 10.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)?
  11. 11.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 9 cm, 1 cm and 9 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 52° and angle B = 41°. What is angle C (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  23. 23.Can a triangle have sides of 10 cm, 22 cm and 10 cm? (a) Yes (b) No
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  28. 28.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)?
  29. 29.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 4 cm, 4 cm and 3 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 87° and angle B = 32°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 56° and 29°. What is the exterior angle (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 7 cm and 21 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?

Answer key

  1. 138
  2. Yes
  3. 49
  4. 57
  5. 33
  6. 53
  7. 50
  8. 56
  9. Yes
  10. 15
  11. 80
  12. 18
  13. 51
  14. 24
  15. 25
  16. 28
  17. Yes
  18. 38
  19. 67
  20. 30
  21. 87
  22. 13
  23. No
  24. 40
  25. 42
  26. 20
  27. 26
  28. 24
  29. 75
  30. 120
  31. 80
  32. 26
  33. 41
  34. Yes
  35. 61
  36. 49
  37. 85
  38. No
  39. 57
  40. 76

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