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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 192 · 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 an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  3. 3.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  4. 4.In triangle ABC, angle A = 78° and angle B = 34°. What is angle C (in degrees)?
  5. 5.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  6. 6.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  8. 8.Can a triangle have sides of 2 cm, 17 cm and 10 cm? (a) Yes (b) No
  9. 9.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 9 cm and 18 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 63° and angle B = 50°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 49° and angle B = 79°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 5 cm, 3 cm and 6 cm? (a) Yes (b) No
  17. 17.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 98° and angle B = 29°. What is angle C (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 69° and 21°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 23° and 32°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 37° and angle B = 22°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 74° and 76°. What is the exterior angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  31. 31.Can a triangle have sides of 7 cm, 10 cm and 5 cm? (a) No (b) Yes
  32. 32.In triangle ABC, angle A = 38° and angle B = 73°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 12 cm, 7 cm and 10 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  40. 40.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?

Answer key

  1. 46
  2. 33
  3. 71
  4. 68
  5. 10
  6. 25
  7. 75
  8. No
  9. 60
  10. No
  11. 67
  12. 54
  13. 30
  14. 58
  15. 52
  16. Yes
  17. 16
  18. 53
  19. 90
  20. 71
  21. 16
  22. 55
  23. 121
  24. 24
  25. 23
  26. 40
  27. 65
  28. 90
  29. 150
  30. 15
  31. Yes
  32. 69
  33. 80
  34. Yes
  35. 92
  36. 55
  37. 45
  38. 80
  39. 27
  40. 9

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