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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 235 · 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 = 92° and angle B = 27°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 94° and angle B = 60°. What is angle C (in degrees)?
  5. 5.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 33° and 71°. What is the exterior angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 6 cm and 8 cm? (a) Yes (b) No
  13. 13.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 63° and 20°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 50° and angle B = 93°. What is angle C (in degrees)?
  19. 19.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)?
  20. 20.Can a triangle have sides of 5 cm, 3 cm and 10 cm? (a) No (b) Yes
  21. 21.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 85° and angle B = 24°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 42° and angle B = 82°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 34° and angle B = 112°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 53° and 63°. What is the exterior angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 2 cm, 11 cm and 6 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 9 cm, 11 cm and 9 cm? (a) No (b) Yes
  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 1 : 2 : 2. What is the biggest angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  35. 35.Can a triangle have sides of 9 cm, 11 cm and 8 cm? (a) Yes (b) No
  36. 36.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 5 cm, 3 cm and 7 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 72° and angle B = 71°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 4 cm, 5 cm and 5 cm? (a) No (b) Yes
  40. 40.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?

Answer key

  1. 61
  2. 100
  3. 66
  4. 26
  5. 4
  6. 120
  7. 61
  8. 17
  9. 64
  10. 104
  11. 57
  12. Yes
  13. 37
  14. 40
  15. 83
  16. 138
  17. 50
  18. 37
  19. 15
  20. No
  21. 25
  22. 20
  23. 36
  24. 71
  25. 40
  26. 56
  27. 34
  28. 116
  29. 30
  30. No
  31. Yes
  32. 20
  33. 72
  34. 30
  35. Yes
  36. 57
  37. Yes
  38. 37
  39. Yes
  40. 82

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