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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 126 · 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 18°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 6 cm, 14 cm and 5 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 50° and angle B = 95°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 17 cm, 6 cm and 9 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 4 cm, 13 cm and 9 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 11 cm, 10 cm and 16 cm? (a) No (b) Yes
  15. 15.In triangle ABC, angle A = 38° and angle B = 24°. What is angle C (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 67° and 32°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 74° and angle B = 26°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 8 cm, 5 cm and 11 cm? (a) Yes (b) No
  21. 21.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  22. 22.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 22° and 35°. What is the exterior angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 59° and angle B = 95°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  28. 28.Can a triangle have sides of 4 cm, 11 cm and 19 cm? (a) No (b) Yes
  29. 29.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 21 cm, 7 cm and 10 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 36° and 38°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 63° and 69°. What is the exterior angle (in degrees)?
  38. 38.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)?
  39. 39.In triangle ABC, angle A = 25° and angle B = 60°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 25° and 21°. What is the exterior angle (in degrees)?

Answer key

  1. 72
  2. 20
  3. 72
  4. 25
  5. 60
  6. No
  7. 35
  8. 46
  9. 94
  10. 39
  11. 39
  12. No
  13. No
  14. Yes
  15. 118
  16. 99
  17. 54
  18. 67
  19. 80
  20. Yes
  21. 74
  22. 70
  23. 140
  24. 57
  25. 56
  26. 26
  27. 40
  28. No
  29. 43
  30. 100
  31. 100
  32. 27
  33. 75
  34. No
  35. 74
  36. 73
  37. 132
  38. 24
  39. 95
  40. 46

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