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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 453 · 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 40°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 31° and angle B = 43°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  5. 5.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  9. 9.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)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 62° and 56°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 10 cm, 14 cm and 7 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  14. 14.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)?
  15. 15.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 97° and angle B = 39°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 20 cm, 9 cm and 11 cm? (a) Yes (b) No
  18. 18.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  19. 19.Can a triangle have sides of 9 cm, 11 cm and 5 cm? (a) Yes (b) No
  20. 20.Can a triangle have sides of 4 cm, 3 cm and 10 cm? (a) Yes (b) No
  21. 21.The two interior opposite angles of a triangle are 65° and 56°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 3 cm, 2 cm and 9 cm? (a) Yes (b) No
  23. 23.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 47° and 42°. What is the exterior angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 53° and 25°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 38° and 46°. What is the exterior angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  29. 29.In triangle ABC, angle A = 93° and angle B = 63°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  31. 31.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)?
  32. 32.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 45° and 58°. What is the exterior angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 49° and 22°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 44° and angle B = 30°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 18 cm, 8 cm and 11 cm? (a) No (b) Yes
  39. 39.In triangle ABC, angle A = 39° and angle B = 94°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?

Answer key

  1. 50
  2. 80
  3. 106
  4. 68
  5. 8
  6. 61
  7. 23
  8. 102
  9. 8
  10. 52
  11. 118
  12. Yes
  13. 77
  14. 24
  15. 79
  16. 44
  17. No
  18. 72
  19. Yes
  20. No
  21. 121
  22. No
  23. 21
  24. 89
  25. 78
  26. 72
  27. 84
  28. 15
  29. 24
  30. 24
  31. 7
  32. 64
  33. 90
  34. 103
  35. 100
  36. 71
  37. 106
  38. Yes
  39. 47
  40. 28

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