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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 409 · 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 angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  3. 3.Can a triangle have sides of 10 cm, 25 cm and 10 cm? (a) Yes (b) No
  4. 4.The two interior opposite angles of a triangle are 47° and 54°. What is the exterior angle (in degrees)?
  5. 5.Can a triangle have sides of 9 cm, 11 cm and 23 cm? (a) No (b) Yes
  6. 6.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)?
  7. 7.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  9. 9.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)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 80° and 52°. What is the exterior angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 69° and 61°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 12 cm, 19 cm and 6 cm? (a) No (b) Yes
  18. 18.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 34° and 71°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  24. 24.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  25. 25.Can a triangle have sides of 11 cm, 10 cm and 13 cm? (a) No (b) Yes
  26. 26.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 33° and 54°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 10 cm and 11 cm? (a) No (b) Yes
  29. 29.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 62° and angle B = 73°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 41° and angle B = 86°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 1 cm, 4 cm and 4 cm? (a) No (b) Yes
  39. 39.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 55° and 44°. What is the exterior angle (in degrees)?

Answer key

  1. 45
  2. 72
  3. No
  4. 101
  5. No
  6. 24
  7. 30
  8. 12
  9. 4
  10. 76
  11. 136
  12. 100
  13. 132
  14. 130
  15. 17
  16. 61
  17. No
  18. 68
  19. 43
  20. 40
  21. 105
  22. 36
  23. 48
  24. 33
  25. Yes
  26. 31
  27. 87
  28. Yes
  29. 37
  30. 120
  31. 74
  32. 104
  33. 45
  34. 72
  35. 19
  36. 90
  37. 53
  38. Yes
  39. 34
  40. 99

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