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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 421 · 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 triangle ABC, angle A = 70° and angle B = 69°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 42° and angle B = 71°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 87° and angle B = 68°. What is angle C (in degrees)?
  7. 7.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)?
  8. 8.In triangle ABC, angle A = 56° and angle B = 47°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 47° and angle B = 97°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 78° and angle B = 34°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 7 cm and 2 cm? (a) Yes (b) No
  17. 17.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 77° and 68°. What is the exterior angle (in degrees)?
  19. 19.Can a triangle have sides of 18 cm, 6 cm and 11 cm? (a) No (b) Yes
  20. 20.In triangle ABC, angle A = 42° and angle B = 78°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  23. 23.Can a triangle have sides of 3 cm, 3 cm and 9 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 92° and angle B = 31°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 55° and angle B = 81°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 74° and 32°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 32° and angle B = 43°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 11 cm, 9 cm and 18 cm? (a) No (b) Yes
  31. 31.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  32. 32.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 41° and angle B = 65°. What is angle C (in degrees)?
  35. 35.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 43° and angle B = 60°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 35° and 43°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  40. 40.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?

Answer key

  1. 41
  2. 73
  3. 67
  4. 35
  5. 13
  6. 25
  7. 15
  8. 77
  9. 72
  10. 24
  11. 36
  12. 68
  13. 41
  14. 59
  15. 76
  16. No
  17. 36
  18. 145
  19. No
  20. 60
  21. 25
  22. 48
  23. No
  24. 57
  25. 130
  26. 44
  27. 106
  28. 105
  29. 51
  30. Yes
  31. 42
  32. 50
  33. 17
  34. 74
  35. 20
  36. 47
  37. 77
  38. 78
  39. 40
  40. 69

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