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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 84 · 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 two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  3. 3.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  4. 4.The two interior opposite angles of a triangle are 73° and 71°. What is the exterior angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 42° and 53°. What is the exterior angle (in degrees)?
  6. 6.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 8 cm and 23 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 48° and angle B = 37°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 68° and angle B = 46°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 66° and 62°. What is the exterior angle (in degrees)?
  12. 12.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)?
  13. 13.The two interior opposite angles of a triangle are 68° and 37°. What is the exterior angle (in degrees)?
  14. 14.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  16. 16.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)?
  17. 17.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 88° and angle B = 49°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 21° and angle B = 110°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 32° and angle B = 85°. 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.Can a triangle have sides of 13 cm, 6 cm and 6 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 20° and angle B = 44°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 34° and angle B = 26°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 49° and angle B = 37°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 90° and angle B = 29°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 46°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 63° and angle B = 35°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  39. 39.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)?
  40. 40.In triangle ABC, angle A = 37° and angle B = 75°. What is angle C (in degrees)?

Answer key

  1. 26
  2. 77
  3. 24
  4. 144
  5. 95
  6. 62
  7. No
  8. 88
  9. 95
  10. 66
  11. 128
  12. 15
  13. 105
  14. 45
  15. 29
  16. 24
  17. 78
  18. 43
  19. 49
  20. 54
  21. 36
  22. Yes
  23. 63
  24. 72
  25. No
  26. 116
  27. 120
  28. 94
  29. 61
  30. 24
  31. 36
  32. 24
  33. 36
  34. 71
  35. 82
  36. 23
  37. 36
  38. 12
  39. 16
  40. 68

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