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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 828 · 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 angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 12 cm and 8 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  4. 4.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  5. 5.Can a triangle have sides of 20 cm, 10 cm and 12 cm? (a) Yes (b) No
  6. 6.In triangle ABC, angle A = 90° and angle B = 61°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 64° and 57°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 3 cm and 12 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  13. 13.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 4 cm, 21 cm and 12 cm? (a) Yes (b) No
  15. 15.The two interior opposite angles of a triangle are 78° and 53°. What is the exterior angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 34° and 59°. What is the exterior angle (in degrees)?
  17. 17.Can a triangle have sides of 5 cm, 13 cm and 6 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 64° and angle B = 68°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  21. 21.Can a triangle have sides of 12 cm, 5 cm and 4 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 72° and angle B = 43°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 65° and 78°. What is the exterior angle (in degrees)?
  25. 25.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 88° and angle B = 34°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  29. 29.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 36° and angle B = 97°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 78° and 77°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 35° and 33°. What is the exterior angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 31° and 46°. What is the exterior angle (in degrees)?

Answer key

  1. 36
  2. Yes
  3. 72
  4. 36
  5. Yes
  6. 29
  7. 121
  8. Yes
  9. 84
  10. 24
  11. 53
  12. 26
  13. 15
  14. No
  15. 131
  16. 93
  17. No
  18. 48
  19. 40
  20. 37
  21. No
  22. 65
  23. 77
  24. 143
  25. 37
  26. 69
  27. 58
  28. 17
  29. 57
  30. 45
  31. 47
  32. 48
  33. 29
  34. 112
  35. 48
  36. 155
  37. 18
  38. 70
  39. 68
  40. 77

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