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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 547 · 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 70°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 5 cm, 10 cm and 5 cm? (a) No (b) Yes
  3. 3.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  4. 4.Can a triangle have sides of 25 cm, 9 cm and 11 cm? (a) No (b) Yes
  5. 5.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)?
  6. 6.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 38° and angle B = 117°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 4 cm and 7 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 91° and angle B = 49°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 76° and angle B = 59°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 41° and angle B = 52°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 12 cm, 5 cm and 9 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 6 cm, 21 cm and 12 cm? (a) No (b) Yes
  20. 20.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)?
  21. 21.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  24. 24.Can a triangle have sides of 2 cm, 3 cm and 5 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 31° and angle B = 33°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 6 cm and 14 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 10 cm and 7 cm? (a) No (b) Yes
  30. 30.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 65° and 71°. What is the exterior angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 45° and 77°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  39. 39.Can a triangle have sides of 21 cm, 7 cm and 10 cm? (a) No (b) Yes
  40. 40.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?

Answer key

  1. 32
  2. No
  3. 72
  4. No
  5. 8
  6. 67
  7. 29
  8. 5
  9. 12
  10. 90
  11. 25
  12. 22
  13. Yes
  14. 40
  15. 80
  16. 45
  17. 87
  18. Yes
  19. No
  20. 7
  21. 72
  22. 39
  23. 36
  24. No
  25. 116
  26. No
  27. 100
  28. 18
  29. Yes
  30. 42
  31. 34
  32. 17
  33. 136
  34. 40
  35. 79
  36. 63
  37. 122
  38. 30
  39. No
  40. 49

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