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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 415 · 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.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 21° and 20°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 67° and 25°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 17 cm, 8 cm and 8 cm? (a) No (b) Yes
  8. 8.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 21 cm and 8 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 50° and angle B = 63°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 10 cm, 22 cm and 12 cm? (a) No (b) Yes
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  16. 16.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)?
  17. 17.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 24 cm, 10 cm and 10 cm? (a) Yes (b) No
  19. 19.The two interior opposite angles of a triangle are 35° and 69°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 55° and angle B = 49°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 65° and angle B = 24°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  26. 26.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 35° and 23°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 58° and angle B = 62°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 31° and angle B = 68°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 84° and angle B = 70°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 72° and 26°. What is the exterior angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  37. 37.In triangle ABC, angle A = 78° and angle B = 39°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 29° and 79°. What is the exterior angle (in degrees)?

Answer key

  1. 75
  2. 54
  3. 41
  4. 92
  5. 62
  6. 45
  7. No
  8. 69
  9. No
  10. 14
  11. 47
  12. 34
  13. 67
  14. No
  15. 70
  16. 24
  17. 39
  18. No
  19. 104
  20. 67
  21. 76
  22. 91
  23. 80
  24. 80
  25. 13
  26. 18
  27. 32
  28. 58
  29. 60
  30. 81
  31. 45
  32. 26
  33. 70
  34. 23
  35. 98
  36. 26
  37. 63
  38. 72
  39. 53
  40. 108

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