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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 243 · 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 = 87° and angle B = 54°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 44°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 61° and angle B = 25°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 2 cm, 12 cm and 7 cm? (a) Yes (b) No
  9. 9.In triangle ABC, angle A = 38° and angle B = 96°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 4 cm and 17 cm? (a) No (b) Yes
  11. 11.The two interior opposite angles of a triangle are 66° and 64°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 62° and angle B = 33°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 20° and angle B = 84°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  20. 20.In triangle ABC, angle A = 33° and angle B = 55°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 23° and angle B = 111°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 48° and 48°. What is the exterior angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  29. 29.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)?
  30. 30.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  32. 32.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)?
  33. 33.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  35. 35.Can a triangle have sides of 3 cm, 7 cm and 8 cm? (a) No (b) Yes
  36. 36.Can a triangle have sides of 8 cm, 6 cm and 5 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 92° and angle B = 28°. What is angle C (in degrees)?
  40. 40.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)?

Answer key

  1. 39
  2. 36
  3. 20
  4. 21
  5. 77
  6. 36
  7. 94
  8. No
  9. 46
  10. No
  11. 130
  12. 85
  13. 16
  14. 13
  15. 59
  16. 70
  17. 46
  18. 76
  19. 69
  20. 92
  21. 46
  22. 75
  23. 96
  24. 5
  25. 74
  26. 32
  27. 21
  28. 12
  29. 8
  30. 45
  31. 20
  32. 7
  33. 12
  34. 45
  35. Yes
  36. Yes
  37. 138
  38. 66
  39. 60
  40. 10

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