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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 384 · 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.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 24 cm, 9 cm and 11 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.Can a triangle have sides of 17 cm, 11 cm and 10 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 4 cm, 3 cm and 6 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 17 cm, 6 cm and 6 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 12 cm, 7 cm and 22 cm? (a) No (b) Yes
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 72° and 24°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  24. 24.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 76° and angle B = 51°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 83° and angle B = 72°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  35. 35.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  36. 36.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?

Answer key

  1. 71
  2. No
  3. 40
  4. 100
  5. 38
  6. 70
  7. 25
  8. Yes
  9. 10
  10. 100
  11. 45
  12. 34
  13. 70
  14. Yes
  15. No
  16. 33
  17. 66
  18. No
  19. 36
  20. 124
  21. 96
  22. 88
  23. 70
  24. 22
  25. 43
  26. 75
  27. 106
  28. 75
  29. 56
  30. 74
  31. 53
  32. 74
  33. 25
  34. 72
  35. 15
  36. 54
  37. 68
  38. 41
  39. 86
  40. 18

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