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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 584 · 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.The two interior opposite angles of a triangle are 22° and 69°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 17 cm, 10 cm and 4 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 30° and 49°. What is the exterior angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 23 cm and 8 cm? (a) No (b) Yes
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 48° and angle B = 35°. What is angle C (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  14. 14.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  15. 15.Can a triangle have sides of 10 cm, 19 cm and 8 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  20. 20.In triangle ABC, angle A = 92° and angle B = 32°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  24. 24.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 4 cm, 4 cm and 4 cm? (a) Yes (b) No
  27. 27.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  29. 29.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)?
  30. 30.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  31. 31.Can a triangle have sides of 22 cm, 11 cm and 7 cm? (a) No (b) Yes
  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.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 31° and angle B = 63°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 32° and angle B = 98°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 8 cm and 6 cm? (a) No (b) Yes

Answer key

  1. 91
  2. No
  3. 14
  4. 27
  5. 79
  6. 45
  7. No
  8. 25
  9. 97
  10. 25
  11. 14
  12. 90
  13. 25
  14. 20
  15. No
  16. 37
  17. 130
  18. 65
  19. 78
  20. 56
  21. 75
  22. 80
  23. 36
  24. 35
  25. 40
  26. Yes
  27. 46
  28. 31
  29. 24
  30. 15
  31. No
  32. 5
  33. 14
  34. 33
  35. 86
  36. 50
  37. 30
  38. 16
  39. 138
  40. Yes

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