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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 999 · 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.Can a triangle have sides of 9 cm, 11 cm and 13 cm? (a) Yes (b) No
  2. 2.The two interior opposite angles of a triangle are 44° and 80°. What is the exterior angle (in degrees)?
  3. 3.Can a triangle have sides of 3 cm, 11 cm and 17 cm? (a) Yes (b) No
  4. 4.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 21 cm and 10 cm? (a) Yes (b) No
  17. 17.Can a triangle have sides of 7 cm, 10 cm and 8 cm? (a) Yes (b) No
  18. 18.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 96° and angle B = 52°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 6 cm, 5 cm and 8 cm? (a) No (b) Yes
  26. 26.Can a triangle have sides of 10 cm, 7 cm and 4 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 3 cm, 11 cm and 10 cm? (a) Yes (b) No
  29. 29.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 11 cm, 14 cm and 6 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 33° and angle B = 35°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  36. 36.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)?
  37. 37.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 23° and angle B = 40°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 70° and angle B = 29°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 12 cm, 21 cm and 9 cm? (a) Yes (b) No

Answer key

  1. Yes
  2. 124
  3. No
  4. 76
  5. 72
  6. 12
  7. 51
  8. 17
  9. 10
  10. 40
  11. 70
  12. 80
  13. 32
  14. 13
  15. 18
  16. No
  17. Yes
  18. 45
  19. 25
  20. 90
  21. 50
  22. 13
  23. 32
  24. 48
  25. Yes
  26. Yes
  27. 73
  28. Yes
  29. 48
  30. 19
  31. 120
  32. 49
  33. Yes
  34. 112
  35. 58
  36. 24
  37. 82
  38. 117
  39. 81
  40. No

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