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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 486 · 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 longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  2. 2.Can a triangle have sides of 4 cm, 6 cm and 10 cm? (a) No (b) Yes
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  6. 6.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  7. 7.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  10. 10.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  11. 11.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  12. 12.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  13. 13.In triangle ABC, angle A = 33° and angle B = 56°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  16. 16.Can a triangle have sides of 9 cm, 10 cm and 5 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  18. 18.Can a triangle have sides of 11 cm, 8 cm and 21 cm? (a) Yes (b) No
  19. 19.In triangle ABC, angle A = 85° and angle B = 47°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 57° and angle B = 49°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 14 cm, 6 cm and 6 cm? (a) No (b) Yes
  23. 23.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 73° and angle B = 32°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 30° and 67°. What is the exterior angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  29. 29.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  35. 35.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 3 cm, 9 cm and 7 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 33° and angle B = 47°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 19 cm and 8 cm? (a) Yes (b) No

Answer key

  1. 7
  2. No
  3. 17
  4. 40
  5. 68
  6. 64
  7. 55
  8. 75
  9. 30
  10. 15
  11. 4
  12. 72
  13. 91
  14. 41
  15. 90
  16. Yes
  17. 15
  18. No
  19. 48
  20. 18
  21. 74
  22. No
  23. 65
  24. 26
  25. 75
  26. 75
  27. 97
  28. 26
  29. 56
  30. 17
  31. 72
  32. 25
  33. 60
  34. 21
  35. 58
  36. Yes
  37. 100
  38. 36
  39. 20
  40. No

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