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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 148 · 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 7 cm, 17 cm and 9 cm? (a) Yes (b) No
  2. 2.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 5 cm, 6 cm and 11 cm? (a) No (b) Yes
  5. 5.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 60° and 47°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 10 cm and 5 cm? (a) Yes (b) No
  9. 9.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 51° and angle B = 53°. What is angle C (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  16. 16.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 51° and angle B = 90°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 4 cm, 12 cm and 10 cm? (a) Yes (b) No
  20. 20.Can a triangle have sides of 22 cm, 9 cm and 9 cm? (a) Yes (b) No
  21. 21.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 27° and angle B = 63°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 65° and 37°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 3 cm, 12 cm and 18 cm? (a) Yes (b) No
  30. 30.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 83° and angle B = 21°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 75° and angle B = 45°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 58° and angle B = 32°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 63° and 70°. What is the exterior angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  37. 37.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 49° and angle B = 40°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 20 cm and 8 cm? (a) No (b) Yes

Answer key

  1. No
  2. 90
  3. 69
  4. No
  5. 54
  6. 24
  7. 107
  8. No
  9. 4
  10. 61
  11. 75
  12. 51
  13. 76
  14. 10
  15. 53
  16. 25
  17. 75
  18. 39
  19. Yes
  20. No
  21. 18
  22. 39
  23. 90
  24. 102
  25. 128
  26. 90
  27. 34
  28. 134
  29. No
  30. 50
  31. 76
  32. 60
  33. 90
  34. 72
  35. 133
  36. 39
  37. 30
  38. 72
  39. 91
  40. No

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