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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 934 · 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.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  2. 2.Can a triangle have sides of 8 cm, 5 cm and 4 cm? (a) Yes (b) No
  3. 3.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 8 cm and 2 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 74° and angle B = 36°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 4 cm and 5 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 33° and 57°. What is the exterior angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 61° and angle B = 81°. What is angle C (in degrees)?
  11. 11.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)?
  12. 12.Can a triangle have sides of 18 cm, 4 cm and 10 cm? (a) No (b) Yes
  13. 13.In triangle ABC, angle A = 35° and angle B = 35°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.The two interior opposite angles of a triangle are 61° and 55°. What is the exterior angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  22. 22.Can a triangle have sides of 20 cm, 10 cm and 8 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 47° and angle B = 29°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 53° and angle B = 61°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 40° and angle B = 43°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 89° and angle B = 22°. What is angle C (in degrees)?
  33. 33.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 24° and 70°. What is the exterior angle (in degrees)?
  35. 35.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)?
  36. 36.Can a triangle have sides of 11 cm, 5 cm and 8 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 93° and angle B = 46°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  39. 39.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)?
  40. 40.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?

Answer key

  1. 90
  2. Yes
  3. 20
  4. Yes
  5. 70
  6. Yes
  7. 19
  8. 90
  9. 74
  10. 38
  11. 15
  12. No
  13. 110
  14. 100
  15. 45
  16. 39
  17. 116
  18. 5
  19. 15
  20. 44
  21. 39
  22. No
  23. 104
  24. 72
  25. 46
  26. 120
  27. 66
  28. 22
  29. 49
  30. 100
  31. 97
  32. 69
  33. 24
  34. 94
  35. 24
  36. Yes
  37. 41
  38. 60
  39. 7
  40. 18

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