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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 983 · 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 19°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 75° and 53°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.Can a triangle have sides of 23 cm, 12 cm and 7 cm? (a) No (b) Yes
  9. 9.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 74° and angle B = 58°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 2 cm, 10 cm and 9 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 56° and angle B = 43°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 47° and angle B = 47°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 58° and angle B = 33°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 86° and angle B = 26°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 7 cm, 9 cm and 21 cm? (a) No (b) Yes
  19. 19.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  20. 20.Can a triangle have sides of 8 cm, 22 cm and 9 cm? (a) Yes (b) No
  21. 21.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 29° and 66°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 8 cm, 9 cm and 15 cm? (a) Yes (b) No
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 28° and angle B = 117°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  30. 30.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)?
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 20 cm, 11 cm and 9 cm? (a) No (b) Yes
  34. 34.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  35. 35.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)?
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 62° and 27°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 91° and angle B = 51°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?

Answer key

  1. 71
  2. 41
  3. 40
  4. 47
  5. 15
  6. 128
  7. 72
  8. No
  9. 71
  10. 78
  11. 48
  12. 66
  13. Yes
  14. 81
  15. 86
  16. 89
  17. 68
  18. No
  19. 14
  20. No
  21. 22
  22. 72
  23. 95
  24. Yes
  25. 80
  26. 116
  27. 48
  28. 35
  29. 100
  30. 4
  31. 54
  32. 130
  33. No
  34. 15
  35. 15
  36. 90
  37. 40
  38. 89
  39. 38
  40. 43

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