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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 221 · 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 = 33° and angle B = 44°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 27° and angle B = 108°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 16 cm, 7 cm and 7 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 13 cm, 3 cm and 12 cm? (a) No (b) Yes
  5. 5.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 71° and angle B = 52°. What is angle C (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.Can a triangle have sides of 10 cm, 19 cm and 10 cm? (a) No (b) Yes
  9. 9.The two interior opposite angles of a triangle are 63° and 79°. What is the exterior angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 44° and 67°. What is the exterior angle (in degrees)?
  11. 11.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  12. 12.Can a triangle have sides of 21 cm, 11 cm and 6 cm? (a) No (b) Yes
  13. 13.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  14. 14.The two interior opposite angles of a triangle are 71° and 28°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 21 cm, 10 cm and 7 cm? (a) No (b) Yes
  17. 17.The two interior opposite angles of a triangle are 68° and 53°. What is the exterior angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 39° and 51°. What is the exterior angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 38° and 43°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 10 cm, 9 cm and 20 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 21° and angle B = 97°. What is angle C (in degrees)?
  29. 29.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  30. 30.In triangle ABC, angle A = 56° and angle B = 88°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.In triangle ABC, angle A = 61° and angle B = 23°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 8 cm and 3 cm? (a) Yes (b) No
  38. 38.The two interior opposite angles of a triangle are 54° and 20°. What is the exterior angle (in degrees)?
  39. 39.Can a triangle have sides of 14 cm, 5 cm and 11 cm? (a) No (b) Yes
  40. 40.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?

Answer key

  1. 103
  2. 45
  3. No
  4. Yes
  5. 72
  6. 57
  7. 29
  8. Yes
  9. 142
  10. 111
  11. 36
  12. No
  13. 5
  14. 99
  15. 12
  16. No
  17. 121
  18. 90
  19. 30
  20. 41
  21. 17
  22. 65
  23. 81
  24. 72
  25. 45
  26. No
  27. 84
  28. 62
  29. 3
  30. 36
  31. 61
  32. 90
  33. 96
  34. 90
  35. 65
  36. 25
  37. Yes
  38. 74
  39. Yes
  40. 77

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