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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 142 · 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 an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 41° and 41°. What is the exterior angle (in degrees)?
  4. 4.Can a triangle have sides of 4 cm, 10 cm and 15 cm? (a) No (b) Yes
  5. 5.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  7. 7.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)?
  8. 8.The two interior opposite angles of a triangle are 41° and 46°. What is the exterior angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 67° and angle B = 29°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 52° and angle B = 59°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 77° and 27°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  19. 19.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 39° and angle B = 31°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 54° and angle B = 35°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 62° and angle B = 69°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 51° and 25°. What is the exterior angle (in degrees)?
  30. 30.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 52° and angle B = 21°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 87° and angle B = 27°. What is angle C (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  36. 36.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)?
  37. 37.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  38. 38.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  39. 39.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?

Answer key

  1. 44
  2. 64
  3. 82
  4. No
  5. 35
  6. 80
  7. 24
  8. 87
  9. 31
  10. 30
  11. 70
  12. 84
  13. 69
  14. 20
  15. 104
  16. 25
  17. 100
  18. 70
  19. 22
  20. 60
  21. 48
  22. 110
  23. 39
  24. 91
  25. 18
  26. 49
  27. 120
  28. 13
  29. 76
  30. 64
  31. 61
  32. 58
  33. 107
  34. 66
  35. 18
  36. 16
  37. 33
  38. 8
  39. 39
  40. 22

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