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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 771 · 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.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 47° and angle B = 41°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 48° and angle B = 34°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 2 cm, 4 cm and 3 cm? (a) No (b) Yes
  8. 8.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  9. 9.In triangle ABC, angle A = 31° and angle B = 49°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 93° and angle B = 27°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 3 cm, 6 cm and 5 cm? (a) No (b) Yes
  14. 14.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 6 cm and 3 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 27 cm, 12 cm and 10 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 63° and angle B = 93°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 77° and angle B = 22°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 74° and angle B = 20°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  26. 26.The two interior opposite angles of a triangle are 42° and 48°. What is the exterior angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  29. 29.In triangle ABC, angle A = 45° and angle B = 69°. What is angle C (in degrees)?
  30. 30.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)?
  31. 31.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  32. 32.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)?
  33. 33.Can a triangle have sides of 6 cm, 4 cm and 6 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 16 cm, 10 cm and 2 cm? (a) Yes (b) No
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 79° and 71°. What is the exterior angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.Can a triangle have sides of 16 cm, 9 cm and 6 cm? (a) No (b) Yes
  40. 40.Can a triangle have sides of 2 cm, 12 cm and 12 cm? (a) No (b) Yes

Answer key

  1. 13
  2. 71
  3. 23
  4. 92
  5. 98
  6. 28
  7. Yes
  8. 15
  9. 100
  10. 60
  11. 55
  12. 36
  13. Yes
  14. 72
  15. No
  16. No
  17. 59
  18. 30
  19. 24
  20. 20
  21. 31
  22. 80
  23. 81
  24. 86
  25. 13
  26. 90
  27. 10
  28. 35
  29. 66
  30. 10
  31. 75
  32. 7
  33. Yes
  34. 69
  35. No
  36. 120
  37. 150
  38. 25
  39. No
  40. Yes

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