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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 500 · 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 an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 48° and angle B = 70°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 45° and 33°. What is the exterior angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 72° and 28°. What is the exterior angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  7. 7.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 9 cm and 8 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 64° and angle B = 80°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 73° and angle B = 70°. What is angle C (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  16. 16.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)?
  17. 17.Can a triangle have sides of 11 cm, 9 cm and 3 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 7 cm and 6 cm? (a) No (b) Yes
  21. 21.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  22. 22.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  23. 23.In triangle ABC, angle A = 72° and angle B = 57°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  26. 26.Can a triangle have sides of 5 cm, 15 cm and 8 cm? (a) No (b) Yes
  27. 27.The two interior opposite angles of a triangle are 66° and 33°. What is the exterior angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 47° and angle B = 93°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 2 cm and 4 cm? (a) Yes (b) No
  31. 31.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 47° and 50°. What is the exterior angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 54° and 80°. What is the exterior angle (in degrees)?
  37. 37.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 24° and angle B = 32°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?

Answer key

  1. 29
  2. 72
  3. 62
  4. 78
  5. 100
  6. 12
  7. 126
  8. Yes
  9. 72
  10. 36
  11. 46
  12. 25
  13. 37
  14. 17
  15. 36
  16. 24
  17. Yes
  18. 63
  19. 17
  20. Yes
  21. 50
  22. 12
  23. 51
  24. 77
  25. 23
  26. No
  27. 99
  28. 136
  29. 40
  30. Yes
  31. 79
  32. 140
  33. 26
  34. 97
  35. 30
  36. 134
  37. 36
  38. 124
  39. 37
  40. 36

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