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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 596 · 40 sums
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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 7 cm, 6 cm and 3 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 5 cm, 2 cm and 4 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 44° and 55°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 11 cm, 7 cm and 5 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 55° and angle B = 29°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 41° and angle B = 27°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 32° and angle B = 42°. What is angle C (in degrees)?
  13. 13.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)?
  14. 14.The two interior opposite angles of a triangle are 29° and 57°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 17 cm, 6 cm and 6 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 30° and angle B = 61°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 10 cm and 9 cm? (a) Yes (b) No
  25. 25.The two interior opposite angles of a triangle are 60° and 69°. What is the exterior angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 44° and 35°. What is the exterior angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 45° and 72°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 4 cm, 2 cm and 3 cm? (a) Yes (b) No
  29. 29.In triangle ABC, angle A = 21° and angle B = 133°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 72° and 79°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 16 cm, 6 cm and 5 cm? (a) No (b) Yes
  32. 32.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  33. 33.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  34. 34.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)?
  35. 35.The two interior opposite angles of a triangle are 50° and 30°. What is the exterior 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.Can a triangle have sides of 3 cm, 7 cm and 9 cm? (a) No (b) Yes
  38. 38.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 68° and 55°. What is the exterior angle (in degrees)?

Answer key

  1. Yes
  2. Yes
  3. 50
  4. 99
  5. 60
  6. 20
  7. 72
  8. 24
  9. Yes
  10. 96
  11. 112
  12. 106
  13. 4
  14. 86
  15. 40
  16. 75
  17. 24
  18. No
  19. 89
  20. 13
  21. 32
  22. 35
  23. 76
  24. Yes
  25. 129
  26. 79
  27. 117
  28. Yes
  29. 26
  30. 151
  31. No
  32. 68
  33. 15
  34. 8
  35. 80
  36. 24
  37. Yes
  38. 38
  39. 90
  40. 123

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