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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 622 · 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 15 cm and 8 cm. How long is the longest side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 2 cm, 2 cm and 3 cm? (a) Yes (b) No
  4. 4.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 2 cm, 3 cm and 8 cm? (a) No (b) Yes
  7. 7.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 23 cm, 12 cm and 6 cm? (a) Yes (b) No
  9. 9.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  10. 10.Can a triangle have sides of 5 cm, 4 cm and 3 cm? (a) Yes (b) No
  11. 11.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 20° and angle B = 120°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  17. 17.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)?
  18. 18.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  20. 20.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  21. 21.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 22° and angle B = 22°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  25. 25.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 48° and angle B = 61°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 97° and angle B = 28°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 91° and angle B = 36°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 34° and 58°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 60° and angle B = 24°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  39. 39.Can a triangle have sides of 8 cm, 19 cm and 9 cm? (a) Yes (b) No
  40. 40.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?

Answer key

  1. 17
  2. 34
  3. Yes
  4. 5
  5. 33
  6. No
  7. 65
  8. No
  9. 58
  10. Yes
  11. 24
  12. 40
  13. 61
  14. 30
  15. 118
  16. 42
  17. 15
  18. 112
  19. 33
  20. 28
  21. 23
  22. 136
  23. 39
  24. 29
  25. 43
  26. 36
  27. 13
  28. 11
  29. 12
  30. 71
  31. 55
  32. 136
  33. 26
  34. 53
  35. 92
  36. 58
  37. 96
  38. 25
  39. No
  40. 56

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