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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 573 · 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.

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  1. 1.In triangle ABC, angle A = 86° and angle B = 44°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 93° and angle B = 48°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  6. 6.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)?
  7. 7.Can a triangle have sides of 8 cm, 13 cm and 4 cm? (a) Yes (b) No
  8. 8.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  9. 9.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) No (b) Yes
  10. 10.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)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  12. 12.In triangle ABC, angle A = 70° and angle B = 59°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 43° and angle B = 104°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 5 cm, 7 cm and 17 cm? (a) No (b) Yes
  20. 20.Can a triangle have sides of 5 cm, 11 cm and 12 cm? (a) No (b) Yes
  21. 21.Can a triangle have sides of 5 cm, 2 cm and 2 cm? (a) No (b) Yes
  22. 22.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 66° and angle B = 66°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 91° and angle B = 44°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  29. 29.Can a triangle have sides of 5 cm, 3 cm and 7 cm? (a) No (b) Yes
  30. 30.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 46° and 37°. What is the exterior angle (in degrees)?
  33. 33.Can a triangle have sides of 2 cm, 3 cm and 4 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 16 cm, 5 cm and 9 cm? (a) Yes (b) No
  35. 35.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 60° and 46°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?

Answer key

  1. 50
  2. 39
  3. 39
  4. 120
  5. 134
  6. 7
  7. No
  8. 25
  9. Yes
  10. 8
  11. 15
  12. 51
  13. 84
  14. 33
  15. 126
  16. 38
  17. 38
  18. 74
  19. No
  20. Yes
  21. No
  22. 20
  23. 72
  24. 48
  25. 45
  26. 90
  27. 8
  28. 74
  29. Yes
  30. 33
  31. 18
  32. 83
  33. Yes
  34. No
  35. 24
  36. 49
  37. 48
  38. 106
  39. 72
  40. 96

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