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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 637 · 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 65°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 5 cm, 15 cm and 12 cm? (a) No (b) Yes
  4. 4.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  5. 5.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  6. 6.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 9 cm and 6 cm? (a) No (b) Yes
  9. 9.Can a triangle have sides of 10 cm, 7 cm and 18 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  14. 14.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)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) Yes (b) No
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 44° and angle B = 27°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 5 cm and 18 cm? (a) No (b) Yes
  21. 21.Can a triangle have sides of 6 cm, 4 cm and 10 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 41° and angle B = 58°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 22° and angle B = 47°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 59° and 68°. What is the exterior angle (in degrees)?
  25. 25.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 55° and angle B = 58°. What is angle C (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 38° and angle B = 55°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  35. 35.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 10 cm and 16 cm? (a) No (b) Yes
  38. 38.Can a triangle have sides of 19 cm, 7 cm and 8 cm? (a) Yes (b) No
  39. 39.The two interior opposite angles of a triangle are 21° and 43°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 19 cm and 11 cm? (a) No (b) Yes

Answer key

  1. 25
  2. 56
  3. Yes
  4. 22
  5. 57
  6. 30
  7. 45
  8. Yes
  9. No
  10. 23
  11. 17
  12. 55
  13. 108
  14. 7
  15. 19
  16. Yes
  17. 120
  18. 109
  19. 22
  20. No
  21. No
  22. 81
  23. 111
  24. 127
  25. 5
  26. 77
  27. 36
  28. 19
  29. 67
  30. 13
  31. 52
  32. 87
  33. 36
  34. 45
  35. 33
  36. 50
  37. No
  38. No
  39. 64
  40. Yes

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