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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 929 · 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.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)?
  2. 2.Can a triangle have sides of 11 cm, 6 cm and 9 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 97° and angle B = 24°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 35° and 55°. What is the exterior angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 58° and 21°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 63° and angle B = 44°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 70° and 49°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 14 cm, 7 cm and 10 cm? (a) No (b) Yes
  9. 9.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 73° and angle B = 39°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 58° and angle B = 83°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 48° and 63°. What is the exterior angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 53° and angle B = 28°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  20. 20.Can a triangle have sides of 4 cm, 8 cm and 12 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  22. 22.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 73° and 65°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 7 cm and 2 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 52° and 58°. What is the exterior angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 12 cm and 2 cm? (a) Yes (b) No
  29. 29.Can a triangle have sides of 7 cm, 4 cm and 15 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 32° and angle B = 66°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 23 cm, 12 cm and 7 cm? (a) No (b) Yes
  32. 32.In triangle ABC, angle A = 53° and angle B = 23°. What is angle C (in degrees)?
  33. 33.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)?
  34. 34.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  35. 35.The two interior opposite angles of a triangle are 32° and 77°. What is the exterior angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  37. 37.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  40. 40.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?

Answer key

  1. 8
  2. Yes
  3. 59
  4. 90
  5. 79
  6. 73
  7. 119
  8. Yes
  9. 24
  10. 72
  11. 68
  12. 13
  13. 39
  14. 111
  15. 25
  16. 90
  17. 99
  18. 26
  19. 29
  20. No
  21. 50
  22. 43
  23. 138
  24. Yes
  25. 42
  26. 110
  27. 102
  28. Yes
  29. No
  30. 82
  31. No
  32. 104
  33. 15
  34. 15
  35. 109
  36. 10
  37. 77
  38. 72
  39. 24
  40. 12

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