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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 745 · 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 11 cm, 4 cm and 8 cm? (a) No (b) Yes
  2. 2.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  3. 3.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 27° and 37°. What is the exterior angle (in degrees)?
  5. 5.Can a triangle have sides of 5 cm, 3 cm and 3 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 89° and angle B = 40°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 54° and angle B = 105°. What is angle C (in degrees)?
  8. 8.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)?
  9. 9.Can a triangle have sides of 7 cm, 2 cm and 3 cm? (a) No (b) Yes
  10. 10.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 21° and angle B = 60°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  14. 14.Can a triangle have sides of 22 cm, 9 cm and 8 cm? (a) Yes (b) No
  15. 15.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)?
  16. 16.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (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 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)?
  19. 19.The two interior opposite angles of a triangle are 38° and 41°. What is the exterior angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 73° and 47°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 22° and angle B = 125°. What is angle C (in degrees)?
  22. 22.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  23. 23.In triangle ABC, angle A = 57° and angle B = 25°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 38° and angle B = 45°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 80° and angle B = 28°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 73° and 58°. What is the exterior angle (in degrees)?
  29. 29.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  30. 30.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)?
  31. 31.In triangle ABC, angle A = 62° and angle B = 97°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 10 cm, 12 cm and 15 cm? (a) Yes (b) No
  34. 34.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 51° and angle B = 85°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 12 cm, 18 cm and 4 cm? (a) No (b) Yes
  38. 38.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 52° and angle B = 43°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?

Answer key

  1. Yes
  2. 25
  3. 73
  4. 64
  5. Yes
  6. 51
  7. 21
  8. 15
  9. No
  10. 54
  11. 99
  12. 90
  13. 57
  14. No
  15. 12
  16. 90
  17. 100
  18. 10
  19. 79
  20. 120
  21. 33
  22. 15
  23. 98
  24. 97
  25. 40
  26. 64
  27. 72
  28. 131
  29. 53
  30. 8
  31. 21
  32. 56
  33. Yes
  34. 96
  35. 40
  36. 44
  37. No
  38. 16
  39. 85
  40. 48

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