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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 423 · 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 12 cm, 25 cm and 9 cm? (a) Yes (b) No
  2. 2.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 43° and 47°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  7. 7.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 64° and angle B = 41°. What is angle C (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.Can a triangle have sides of 7 cm, 10 cm and 21 cm? (a) Yes (b) No
  12. 12.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 41° and 21°. What is the exterior angle (in degrees)?
  16. 16.In triangle ABC, angle A = 40° and angle B = 55°. What is angle C (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.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)?
  19. 19.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)?
  20. 20.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  22. 22.In triangle ABC, angle A = 40° and angle B = 40°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  24. 24.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)?
  25. 25.The two interior opposite angles of a triangle are 45° and 24°. What is the exterior angle (in degrees)?
  26. 26.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 41° and angle B = 75°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 99° and angle B = 26°. What is angle C (in degrees)?
  31. 31.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 63° and angle B = 77°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 62° and angle B = 69°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 46° and 37°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  40. 40.Can a triangle have sides of 10 cm, 8 cm and 5 cm? (a) No (b) Yes

Answer key

  1. No
  2. 73
  3. 72
  4. 90
  5. 54
  6. 45
  7. 59
  8. 12
  9. 75
  10. 36
  11. No
  12. 30
  13. 15
  14. 58
  15. 62
  16. 85
  17. 39
  18. 7
  19. 24
  20. 26
  21. 17
  22. 100
  23. 23
  24. 8
  25. 69
  26. 22
  27. 42
  28. 64
  29. 90
  30. 55
  31. 15
  32. 40
  33. 44
  34. 96
  35. 15
  36. 49
  37. 83
  38. 12
  39. 30
  40. Yes

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