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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 201 · 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 angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 7 cm and 13 cm? (a) Yes (b) No
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  4. 4.Can a triangle have sides of 6 cm, 4 cm and 2 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 80° and 44°. What is the exterior angle (in degrees)?
  7. 7.Can a triangle have sides of 8 cm, 8 cm and 17 cm? (a) No (b) Yes
  8. 8.In triangle ABC, angle A = 77° and angle B = 51°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 68° and angle B = 48°. What is angle C (in degrees)?
  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 73°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  12. 12.Can a triangle have sides of 10 cm, 11 cm and 2 cm? (a) No (b) Yes
  13. 13.In triangle ABC, angle A = 45° and angle B = 44°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 18 cm, 6 cm and 11 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  18. 18.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 25° and angle B = 26°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  22. 22.Can a triangle have sides of 18 cm, 10 cm and 10 cm? (a) No (b) Yes
  23. 23.The two interior opposite angles of a triangle are 61° and 65°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 54° and angle B = 95°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  26. 26.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 12 cm, 18 cm and 6 cm? (a) No (b) Yes
  28. 28.Can a triangle have sides of 9 cm, 17 cm and 8 cm? (a) No (b) Yes
  29. 29.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  30. 30.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  36. 36.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)?
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 32° and angle B = 59°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 79° and 32°. What is the exterior angle (in degrees)?

Answer key

  1. 45
  2. Yes
  3. 48
  4. No
  5. 126
  6. 124
  7. No
  8. 52
  9. 64
  10. 15
  11. 42
  12. Yes
  13. 91
  14. 64
  15. 27
  16. No
  17. 35
  18. 27
  19. 129
  20. 40
  21. 6
  22. Yes
  23. 126
  24. 31
  25. 25
  26. 40
  27. No
  28. No
  29. 18
  30. 53
  31. 43
  32. 20
  33. 80
  34. 49
  35. 20
  36. 24
  37. 20
  38. 70
  39. 89
  40. 111

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