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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 275 · 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 19 cm? (a) No (b) Yes
  2. 2.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  5. 5.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)?
  6. 6.In triangle ABC, angle A = 58° and angle B = 94°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 20° and angle B = 76°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 22 cm, 7 cm and 12 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 7 cm, 7 cm and 6 cm? (a) No (b) Yes
  17. 17.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  20. 20.Can a triangle have sides of 2 cm, 9 cm and 12 cm? (a) Yes (b) No
  21. 21.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  24. 24.An exterior angle of a triangle is 156°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  29. 29.Can a triangle have sides of 2 cm, 13 cm and 10 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 5 cm, 2 cm and 4 cm? (a) No (b) Yes
  31. 31.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 31° and angle B = 86°. What is angle C (in degrees)?
  36. 36.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)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 37° and angle B = 110°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  40. 40.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?

Answer key

  1. No
  2. 45
  3. 49
  4. 67
  5. 24
  6. 28
  7. 40
  8. 64
  9. 29
  10. 36
  11. 120
  12. 84
  13. 34
  14. No
  15. 86
  16. Yes
  17. 20
  18. 49
  19. 20
  20. No
  21. 19
  22. 40
  23. 49
  24. 76
  25. 76
  26. 74
  27. 15
  28. 24
  29. No
  30. Yes
  31. 70
  32. 61
  33. 50
  34. 18
  35. 63
  36. 8
  37. 90
  38. 33
  39. 15
  40. 74

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