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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 581 · 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.Can a triangle have sides of 7 cm, 12 cm and 7 cm? (a) Yes (b) No
  2. 2.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 8 cm, 19 cm and 7 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  8. 8.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)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  10. 10.Can a triangle have sides of 4 cm, 4 cm and 8 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 90° and angle B = 56°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 81° and angle B = 41°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 70° and angle B = 86°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 40° and angle B = 38°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  29. 29.Can a triangle have sides of 17 cm, 6 cm and 11 cm? (a) No (b) Yes
  30. 30.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 37° and 77°. What is the exterior angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  38. 38.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?

Answer key

  1. Yes
  2. 62
  3. 19
  4. 18
  5. 48
  6. No
  7. 90
  8. 24
  9. 30
  10. No
  11. 34
  12. 45
  13. 104
  14. 98
  15. 57
  16. 58
  17. 100
  18. 80
  19. 24
  20. 77
  21. 120
  22. 22
  23. 82
  24. 102
  25. 26
  26. 20
  27. 72
  28. 45
  29. No
  30. 32
  31. 90
  32. 90
  33. 114
  34. 138
  35. 38
  36. 34
  37. 71
  38. 41
  39. 59
  40. 29

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