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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 631 · 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 two equal angles are 67° each. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 34° and 31°. What is the exterior angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  5. 5.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 11 cm and 17 cm? (a) Yes (b) No
  8. 8.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 3 cm, 10 cm and 10 cm? (a) No (b) Yes
  15. 15.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 57° and angle B = 101°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 57° and 63°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 8 cm, 7 cm and 9 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 22° and angle B = 63°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 6 cm, 10 cm and 16 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 7 cm and 18 cm? (a) No (b) Yes
  30. 30.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 16 cm, 10 cm and 10 cm? (a) No (b) Yes
  32. 32.Can a triangle have sides of 7 cm, 7 cm and 16 cm? (a) No (b) Yes
  33. 33.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)?
  34. 34.In triangle ABC, angle A = 80° and angle B = 73°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 10 cm and 21 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 69° and 44°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 36° and angle B = 105°. What is angle C (in degrees)?

Answer key

  1. 46
  2. 65
  3. 100
  4. 28
  5. 50
  6. 53
  7. Yes
  8. 38
  9. 66
  10. 17
  11. 90
  12. 20
  13. 25
  14. Yes
  15. 70
  16. 22
  17. 34
  18. 51
  19. 120
  20. Yes
  21. 26
  22. 21
  23. 39
  24. 27
  25. 95
  26. 90
  27. No
  28. 45
  29. No
  30. 98
  31. Yes
  32. No
  33. 36
  34. 27
  35. No
  36. 57
  37. 113
  38. 90
  39. 57
  40. 39

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