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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 162 · 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.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 9 cm, 8 cm and 21 cm? (a) Yes (b) No
  6. 6.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 26° and 68°. What is the exterior angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 31° and 46°. What is the exterior angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  12. 12.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 14 cm and 7 cm? (a) Yes (b) No
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  19. 19.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  20. 20.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 83° and angle B = 52°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 96° and angle B = 62°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 2 cm, 9 cm and 15 cm? (a) No (b) Yes
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  25. 25.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 3 cm, 5 cm and 5 cm? (a) Yes (b) No
  27. 27.In triangle ABC, angle A = 76° and angle B = 23°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 50° and angle B = 70°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 12 cm, 4 cm and 7 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 68° and angle B = 20°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (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 an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  37. 37.Can a triangle have sides of 13 cm, 6 cm and 10 cm? (a) Yes (b) No
  38. 38.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  39. 39.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)?
  40. 40.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?

Answer key

  1. 7
  2. 70
  3. 47
  4. 39
  5. No
  6. 75
  7. 74
  8. 26
  9. 94
  10. 77
  11. 5
  12. 90
  13. No
  14. 40
  15. 74
  16. 58
  17. 72
  18. 26
  19. 72
  20. 58
  21. 45
  22. 22
  23. No
  24. 25
  25. 29
  26. Yes
  27. 81
  28. 104
  29. 60
  30. No
  31. 92
  32. 37
  33. 64
  34. 72
  35. 10
  36. 84
  37. Yes
  38. 24
  39. 24
  40. 20

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