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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 620 · 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 10 cm, 25 cm and 11 cm? (a) No (b) Yes
  2. 2.Can a triangle have sides of 9 cm, 12 cm and 20 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 14 cm, 5 cm and 7 cm? (a) Yes (b) No
  4. 4.Can a triangle have sides of 8 cm, 7 cm and 15 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 79° and 34°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  13. 13.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 37° and angle B = 42°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 3 cm, 2 cm and 3 cm? (a) No (b) Yes
  20. 20.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 20 cm, 8 cm and 7 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 74° and angle B = 55°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 26° and angle B = 66°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 64° and 70°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.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)?
  31. 31.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 56° and 57°. What is the exterior angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  37. 37.The two interior opposite angles of a triangle are 67° and 26°. What is the exterior angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 8 cm and 7 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?

Answer key

  1. No
  2. Yes
  3. No
  4. No
  5. 42
  6. 113
  7. 72
  8. 26
  9. 39
  10. 48
  11. 75
  12. 45
  13. 67
  14. 63
  15. 90
  16. 77
  17. 101
  18. 25
  19. Yes
  20. 46
  21. 100
  22. 36
  23. 26
  24. No
  25. 51
  26. 88
  27. 134
  28. 72
  29. 25
  30. 7
  31. 39
  32. 5
  33. 113
  34. 16
  35. 40
  36. 17
  37. 93
  38. 10
  39. Yes
  40. 18

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