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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 941 · 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 a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 18 cm, 6 cm and 10 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 4 cm, 2 cm and 9 cm? (a) No (b) Yes
  4. 4.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  5. 5.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)?
  6. 6.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  9. 9.Can a triangle have sides of 23 cm, 8 cm and 12 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 8 cm. How long is the third side (in cm)?
  11. 11.The two interior opposite angles of a triangle are 60° and 77°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 9 cm and 14 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 12 cm, 10 cm and 26 cm? (a) No (b) Yes
  14. 14.The two interior opposite angles of a triangle are 34° and 35°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 34° and angle B = 124°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 23° and angle B = 69°. What is angle C (in degrees)?
  17. 17.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  18. 18.In triangle ABC, angle A = 74° and angle B = 37°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 34° and 75°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 73° and angle B = 50°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 15 cm, 6 cm and 6 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 62° and angle B = 69°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 5 cm and 5 cm? (a) Yes (b) No
  26. 26.Can a triangle have sides of 15 cm, 8 cm and 4 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) No (b) Yes
  28. 28.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 61° and 30°. What is the exterior angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 90° and angle B = 36°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 80° and angle B = 54°. What is angle C (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 31° and 45°. What is the exterior angle (in degrees)?
  40. 40.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)?

Answer key

  1. 63
  2. No
  3. No
  4. 100
  5. 15
  6. 49
  7. 50
  8. 20
  9. No
  10. 15
  11. 137
  12. Yes
  13. No
  14. 69
  15. 22
  16. 88
  17. 10
  18. 69
  19. 72
  20. 109
  21. 57
  22. No
  23. 49
  24. 38
  25. Yes
  26. No
  27. No
  28. 35
  29. 67
  30. 91
  31. 40
  32. 54
  33. 39
  34. 61
  35. 36
  36. 26
  37. 20
  38. 46
  39. 76
  40. 7

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