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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 904 · 40 sums
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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 2 cm, 14 cm and 10 cm? (a) No (b) Yes
  2. 2.Can a triangle have sides of 11 cm, 10 cm and 10 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 43° and angle B = 43°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 44° and angle B = 100°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 68° and 35°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 53° and angle B = 44°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 36° and angle B = 41°. What is angle C (in degrees)?
  10. 10.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)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 49° and 31°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 8 cm, 2 cm and 7 cm? (a) No (b) Yes
  14. 14.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)?
  15. 15.In triangle ABC, angle A = 24° and angle B = 52°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 3 cm, 3 cm and 10 cm? (a) No (b) Yes
  19. 19.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  20. 20.Can a triangle have sides of 7 cm, 3 cm and 9 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 52° and 57°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 83° and angle B = 42°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 13 cm, 8 cm and 6 cm? (a) Yes (b) No
  26. 26.Can a triangle have sides of 6 cm, 6 cm and 6 cm? (a) Yes (b) No
  27. 27.Can a triangle have sides of 4 cm, 10 cm and 12 cm? (a) No (b) Yes
  28. 28.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 82° and angle B = 46°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 24 cm and 12 cm? (a) No (b) Yes
  31. 31.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 15 cm, 8 cm and 6 cm? (a) Yes (b) No
  33. 33.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.Can a triangle have sides of 25 cm, 10 cm and 12 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 26° and 21°. What is the exterior angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  37. 37.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  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 = 70° and angle B = 33°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?

Answer key

  1. No
  2. Yes
  3. 94
  4. 49
  5. 36
  6. 103
  7. 69
  8. 83
  9. 103
  10. 24
  11. 54
  12. 80
  13. Yes
  14. 8
  15. 104
  16. 90
  17. 17
  18. No
  19. 56
  20. Yes
  21. 68
  22. 100
  23. 109
  24. 55
  25. Yes
  26. Yes
  27. Yes
  28. 86
  29. 52
  30. No
  31. 26
  32. No
  33. 39
  34. No
  35. 47
  36. 10
  37. 37
  38. 16
  39. 77
  40. 14

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