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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 46 · 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 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  2. 2.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 27° and 20°. What is the exterior angle (in degrees)?
  4. 4.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)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 27° and 21°. What is the exterior angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 85° and angle B = 40°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 9 cm and 6 cm? (a) No (b) Yes
  11. 11.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)?
  12. 12.The two interior opposite angles of a triangle are 27° and 28°. What is the exterior angle (in degrees)?
  13. 13.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 97° and angle B = 49°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 66° and 66°. What is the exterior angle (in degrees)?
  18. 18.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 65° and angle B = 30°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 15 cm, 9 cm and 6 cm? (a) Yes (b) No
  21. 21.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest 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.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)?
  26. 26.Can a triangle have sides of 3 cm, 10 cm and 10 cm? (a) No (b) Yes
  27. 27.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  29. 29.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)?
  30. 30.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) Yes (b) No
  32. 32.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 50° and 29°. What is the exterior angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 90° and angle B = 41°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 45°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?

Answer key

  1. 12
  2. 39
  3. 47
  4. 10
  5. 51
  6. 48
  7. 18
  8. 90
  9. 55
  10. Yes
  11. 15
  12. 55
  13. 32
  14. 15
  15. 34
  16. 36
  17. 132
  18. 44
  19. 85
  20. No
  21. 79
  22. 25
  23. 100
  24. 26
  25. 24
  26. Yes
  27. 24
  28. 25
  29. 7
  30. 58
  31. Yes
  32. 68
  33. 10
  34. 79
  35. 96
  36. 40
  37. 49
  38. 24
  39. 72
  40. 15

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