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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 489 · 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.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  2. 2.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  3. 3.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)?
  4. 4.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 84° and angle B = 29°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  8. 8.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  11. 11.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)?
  12. 12.Can a triangle have sides of 2 cm, 4 cm and 10 cm? (a) No (b) Yes
  13. 13.Can a triangle have sides of 7 cm, 12 cm and 3 cm? (a) No (b) Yes
  14. 14.Can a triangle have sides of 8 cm, 20 cm and 8 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 46°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  17. 17.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  18. 18.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  19. 19.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  20. 20.Can a triangle have sides of 24 cm, 11 cm and 10 cm? (a) Yes (b) No
  21. 21.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  25. 25.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 21 cm and 10 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 35° and angle B = 43°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 98° and angle B = 48°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 9 cm, 9 cm and 23 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 7 cm, 2 cm and 8 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 5 cm, 6 cm and 11 cm? (a) Yes (b) No
  35. 35.Can a triangle have sides of 12 cm, 7 cm and 8 cm? (a) Yes (b) No
  36. 36.The two interior opposite angles of a triangle are 45° and 74°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  40. 40.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?

Answer key

  1. 47
  2. 74
  3. 4
  4. 52
  5. 67
  6. 39
  7. 22
  8. 56
  9. 21
  10. 72
  11. 24
  12. No
  13. No
  14. No
  15. 118
  16. 26
  17. 44
  18. 5
  19. 17
  20. No
  21. 62
  22. 75
  23. 30
  24. 24
  25. 44
  26. No
  27. 102
  28. 60
  29. 76
  30. 44
  31. 34
  32. No
  33. Yes
  34. No
  35. Yes
  36. 119
  37. 64
  38. 66
  39. 3
  40. 77

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