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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 371 · 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 = 99° and angle B = 39°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 65° and angle B = 65°. What is angle C (in degrees)?
  4. 4.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)?
  5. 5.Can a triangle have sides of 7 cm, 9 cm and 3 cm? (a) No (b) Yes
  6. 6.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 12 cm, 10 cm and 3 cm? (a) No (b) Yes
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest 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 a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  11. 11.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)?
  12. 12.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 86° and angle B = 54°. What is angle C (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 65° and 74°. What is the exterior angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  18. 18.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 2 cm and 11 cm? (a) No (b) Yes
  20. 20.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 48° and angle B = 34°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  25. 25.Can a triangle have sides of 3 cm, 5 cm and 3 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 39° and angle B = 103°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 65° and 40°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 42° and 21°. What is the exterior angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  33. 33.Can a triangle have sides of 9 cm, 19 cm and 10 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 9 cm, 4 cm and 9 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 23° and angle B = 39°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  40. 40.Can a triangle have sides of 6 cm, 14 cm and 6 cm? (a) Yes (b) No

Answer key

  1. 42
  2. 42
  3. 50
  4. 9
  5. Yes
  6. 46
  7. Yes
  8. 45
  9. 8
  10. 22
  11. 15
  12. 37
  13. 72
  14. 23
  15. 40
  16. 139
  17. 25
  18. 22
  19. Yes
  20. 60
  21. 21
  22. 98
  23. 30
  24. 13
  25. Yes
  26. 38
  27. 68
  28. 105
  29. 120
  30. 63
  31. 84
  32. 30
  33. No
  34. Yes
  35. 118
  36. 59
  37. 22
  38. 26
  39. 74
  40. No

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