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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 414 · 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 longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  2. 2.Can a triangle have sides of 5 cm, 11 cm and 4 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 86° and angle B = 57°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 30° and angle B = 97°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 2 cm, 9 cm and 9 cm? (a) No (b) Yes
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  9. 9.Can a triangle have sides of 5 cm, 5 cm and 2 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 2 cm, 11 cm and 11 cm? (a) Yes (b) No
  13. 13.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.Can a triangle have sides of 12 cm, 3 cm and 19 cm? (a) No (b) Yes
  18. 18.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  19. 19.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)?
  20. 20.Can a triangle have sides of 7 cm, 8 cm and 4 cm? (a) No (b) Yes
  21. 21.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 51° and angle B = 105°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 97° and angle B = 45°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 11 cm, 21 cm and 8 cm? (a) No (b) Yes
  26. 26.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  33. 33.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)?
  34. 34.In triangle ABC, angle A = 42° and angle B = 85°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 3 cm, 7 cm and 4 cm? (a) Yes (b) No
  36. 36.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 56° and angle B = 58°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 2 cm and 6 cm? (a) Yes (b) No

Answer key

  1. 12
  2. No
  3. 37
  4. 39
  5. 53
  6. 16
  7. Yes
  8. 90
  9. Yes
  10. 71
  11. 80
  12. Yes
  13. 43
  14. 65
  15. 17
  16. 36
  17. No
  18. 17
  19. 8
  20. Yes
  21. 18
  22. 21
  23. 24
  24. 38
  25. No
  26. 72
  27. 25
  28. 34
  29. 14
  30. 75
  31. 72
  32. 29
  33. 7
  34. 53
  35. No
  36. 49
  37. 84
  38. 66
  39. 28
  40. No

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