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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 989 · 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 8 cm, 3 cm and 15 cm? (a) Yes (b) No
  2. 2.In triangle ABC, angle A = 94° and angle B = 20°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  7. 7.In triangle ABC, angle A = 85° and angle B = 39°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  9. 9.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 79° and angle B = 64°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 24° and angle B = 80°. What is angle C (in degrees)?
  14. 14.An exterior angle of a triangle is 148°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  16. 16.Can a triangle have sides of 13 cm, 9 cm and 10 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 12 cm, 10 cm and 17 cm? (a) Yes (b) No
  19. 19.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  21. 21.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  22. 22.Can a triangle have sides of 3 cm, 18 cm and 11 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 26° and angle B = 76°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 100° and angle B = 28°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 89° and angle B = 55°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  29. 29.Can a triangle have sides of 2 cm, 7 cm and 8 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 6 cm, 19 cm and 10 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 39° and angle B = 26°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  35. 35.In triangle ABC, angle A = 37° and angle B = 53°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 65° and angle B = 42°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 43° and angle B = 51°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  40. 40.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?

Answer key

  1. No
  2. 66
  3. 61
  4. 48
  5. 45
  6. 13
  7. 56
  8. 50
  9. 45
  10. 37
  11. 20
  12. 43
  13. 76
  14. 68
  15. 18
  16. Yes
  17. 96
  18. Yes
  19. 20
  20. 54
  21. 72
  22. No
  23. 29
  24. 13
  25. 78
  26. 52
  27. 36
  28. 73
  29. Yes
  30. No
  31. 115
  32. 66
  33. 72
  34. 8
  35. 90
  36. 73
  37. 77
  38. 86
  39. 72
  40. 30

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