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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 841 · 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 6 cm and 8 cm. How long is the longest side (in cm)?
  2. 2.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  6. 6.In triangle ABC, angle A = 74° and angle B = 80°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 82° and angle B = 29°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 26° and angle B = 21°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 78° and angle B = 36°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 26° and angle B = 50°. What is angle C (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  16. 16.Can a triangle have sides of 6 cm, 12 cm and 17 cm? (a) Yes (b) No
  17. 17.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 10 cm and 18 cm? (a) Yes (b) No
  20. 20.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 70° and angle B = 36°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 65° and angle B = 48°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  24. 24.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)?
  25. 25.In triangle ABC, angle A = 23° and angle B = 126°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 54° and 64°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 20° and angle B = 99°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 25° and 75°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 44° and 27°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 13 cm and 9 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  40. 40.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) Yes (b) No

Answer key

  1. 10
  2. 26
  3. 15
  4. 52
  5. 14
  6. 26
  7. 40
  8. 69
  9. 34
  10. 133
  11. 58
  12. 66
  13. 65
  14. 104
  15. 25
  16. Yes
  17. 90
  18. 50
  19. Yes
  20. 73
  21. 74
  22. 67
  23. 54
  24. 10
  25. 31
  26. 20
  27. 76
  28. 118
  29. 13
  30. 31
  31. 61
  32. 42
  33. 100
  34. 71
  35. 59
  36. 62
  37. 68
  38. Yes
  39. 49
  40. Yes

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