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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 31 · 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 9 cm, 10 cm and 10 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 80° and angle B = 27°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 96° and angle B = 44°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 57° and angle B = 32°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 9 cm, 15 cm and 2 cm? (a) No (b) Yes
  12. 12.Can a triangle have sides of 14 cm, 6 cm and 6 cm? (a) Yes (b) No
  13. 13.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  15. 15.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  16. 16.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  17. 17.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)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 55° and 78°. What is the exterior angle (in degrees)?
  21. 21.Can a triangle have sides of 7 cm, 19 cm and 11 cm? (a) Yes (b) No
  22. 22.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 59° and angle B = 41°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.The two interior opposite angles of a triangle are 40° and 25°. What is the exterior angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  27. 27.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 35° and angle B = 94°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 58° and 21°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 94° and angle B = 25°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 84° and angle B = 72°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 24 cm, 12 cm and 7 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  40. 40.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)?

Answer key

  1. Yes
  2. 118
  3. 32
  4. 90
  5. 25
  6. 69
  7. 73
  8. 48
  9. 40
  10. 91
  11. No
  12. No
  13. 10
  14. 41
  15. 71
  16. 7
  17. 8
  18. 36
  19. 19
  20. 133
  21. No
  22. 76
  23. 80
  24. 25
  25. 65
  26. 17
  27. 40
  28. 51
  29. 45
  30. 65
  31. 32
  32. 68
  33. 84
  34. 79
  35. 61
  36. 24
  37. No
  38. 30
  39. 43
  40. 15

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