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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 956 · 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 35°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 61° and 44°. What is the exterior angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  4. 4.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 68° and angle B = 32°. 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.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 99° and angle B = 35°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 7 cm, 17 cm and 9 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 9 cm, 3 cm and 5 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 53° and angle B = 78°. What is angle C (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 45° and 55°. What is the exterior angle (in degrees)?
  16. 16.In triangle ABC, angle A = 88° and angle B = 61°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 29° and angle B = 47°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  19. 19.In triangle ABC, angle A = 54° and angle B = 31°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 54° and angle B = 45°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 6 cm, 10 cm and 21 cm? (a) No (b) Yes
  27. 27.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  28. 28.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  29. 29.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  31. 31.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  32. 32.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 24° and 78°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 25° and angle B = 38°. What is angle C (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 48° and angle B = 82°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?

Answer key

  1. 55
  2. 105
  3. 39
  4. 72
  5. 90
  6. 80
  7. 40
  8. 25
  9. 46
  10. 64
  11. 90
  12. No
  13. No
  14. 49
  15. 100
  16. 31
  17. 104
  18. 15
  19. 95
  20. 26
  21. 60
  22. 27
  23. 45
  24. 38
  25. 81
  26. No
  27. 47
  28. 20
  29. 5
  30. 73
  31. 34
  32. 20
  33. 10
  34. 102
  35. 68
  36. 117
  37. 39
  38. 70
  39. 50
  40. 79

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