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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 357 · 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 116°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  4. 4.Can a triangle have sides of 2 cm, 8 cm and 9 cm? (a) No (b) Yes
  5. 5.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 18 cm, 7 cm and 7 cm? (a) Yes (b) No
  8. 8.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 7 cm and 17 cm? (a) No (b) Yes
  11. 11.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  12. 12.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 25° and angle B = 101°. What is angle C (in degrees)?
  14. 14.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)?
  15. 15.Can a triangle have sides of 19 cm, 11 cm and 4 cm? (a) Yes (b) No
  16. 16.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  17. 17.In triangle ABC, angle A = 90° and angle B = 68°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 14 cm and 4 cm? (a) Yes (b) No
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 24° and angle B = 53°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 63° and 53°. What is the exterior angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 37° and angle B = 36°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 75° and angle B = 48°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 53° and angle B = 86°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  33. 33.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)?
  34. 34.Can a triangle have sides of 19 cm, 9 cm and 9 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 66° and 63°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 56° and angle B = 86°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?

Answer key

  1. 66
  2. 90
  3. 75
  4. Yes
  5. 100
  6. 46
  7. No
  8. 40
  9. 33
  10. No
  11. 22
  12. 46
  13. 54
  14. 15
  15. No
  16. 5
  17. 22
  18. No
  19. 20
  20. 88
  21. 103
  22. 72
  23. 116
  24. 17
  25. 23
  26. 107
  27. 57
  28. 39
  29. 40
  30. 41
  31. 71
  32. 63
  33. 7
  34. No
  35. 75
  36. 100
  37. 70
  38. 129
  39. 38
  40. 17

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