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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 225 · 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 = 88° and angle B = 27°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 47°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  4. 4.In triangle ABC, angle A = 99° and angle B = 38°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 71° and 50°. What is the exterior angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 3 cm and 17 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 22 cm, 8 cm and 12 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 29° and angle B = 93°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 57° and angle B = 43°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 7 cm, 7 cm and 3 cm? (a) No (b) Yes
  20. 20.In triangle ABC, angle A = 91° and angle B = 66°. What is angle C (in degrees)?
  21. 21.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)?
  22. 22.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 77° and angle B = 36°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 23° and angle B = 39°. What is angle C (in degrees)?
  28. 28.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  29. 29.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In triangle ABC, angle A = 53° and angle B = 23°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 3 cm, 3 cm and 4 cm? (a) Yes (b) No
  34. 34.The two interior opposite angles of a triangle are 80° and 23°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 97° and angle B = 31°. What is angle C (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  37. 37.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 55° and angle B = 93°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 82° and angle B = 53°. What is angle C (in degrees)?

Answer key

  1. 65
  2. 72
  3. 23
  4. 43
  5. 50
  6. 63
  7. 121
  8. 70
  9. No
  10. 16
  11. No
  12. 12
  13. 130
  14. 80
  15. 35
  16. 58
  17. 14
  18. 80
  19. Yes
  20. 23
  21. 20
  22. 106
  23. 67
  24. 40
  25. 80
  26. 21
  27. 118
  28. 8
  29. 26
  30. 104
  31. 79
  32. 45
  33. Yes
  34. 103
  35. 52
  36. 10
  37. 34
  38. 32
  39. 55
  40. 45

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