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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 393 · 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.In triangle ABC, angle A = 43° and angle B = 103°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 2 cm, 11 cm and 12 cm? (a) No (b) Yes
  3. 3.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)?
  4. 4.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  6. 6.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)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 11 cm, 17 cm and 5 cm? (a) Yes (b) No
  11. 11.Can a triangle have sides of 12 cm, 19 cm and 5 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  13. 13.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  14. 14.In triangle ABC, angle A = 97° and angle B = 27°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  16. 16.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)?
  17. 17.The two interior opposite angles of a triangle are 47° and 74°. What is the exterior angle (in degrees)?
  18. 18.In triangle ABC, angle A = 39° and angle B = 88°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  22. 22.Can a triangle have sides of 12 cm, 4 cm and 7 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 99° and angle B = 33°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 8 cm and 22 cm? (a) Yes (b) No
  28. 28.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  31. 31.Can a triangle have sides of 8 cm, 11 cm and 2 cm? (a) Yes (b) No
  32. 32.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 93° and angle B = 30°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  37. 37.Can a triangle have sides of 20 cm, 3 cm and 12 cm? (a) No (b) Yes
  38. 38.Can a triangle have sides of 11 cm, 25 cm and 10 cm? (a) No (b) Yes
  39. 39.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 88° and angle B = 23°. What is angle C (in degrees)?

Answer key

  1. 34
  2. Yes
  3. 15
  4. 45
  5. 17
  6. 8
  7. 76
  8. 82
  9. 79
  10. No
  11. No
  12. 46
  13. 3
  14. 56
  15. 90
  16. 18
  17. 121
  18. 53
  19. 33
  20. 45
  21. 10
  22. No
  23. 48
  24. 14
  25. 65
  26. 90
  27. No
  28. 90
  29. 54
  30. 72
  31. No
  32. 25
  33. 57
  34. 47
  35. 31
  36. 26
  37. No
  38. No
  39. 20
  40. 69

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