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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 488 · 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 two equal angles are 35° each. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 6 cm, 8 cm and 7 cm? (a) No (b) Yes
  5. 5.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  6. 6.Can a triangle have sides of 8 cm, 17 cm and 7 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 54° and 79°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 5 cm, 19 cm and 11 cm? (a) Yes (b) No
  9. 9.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  13. 13.In triangle ABC, angle A = 90° and angle B = 41°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 42° and angle B = 53°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 66° and angle B = 43°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  19. 19.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)?
  20. 20.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 54° and 30°. What is the exterior angle (in degrees)?
  23. 23.Can a triangle have sides of 10 cm, 9 cm and 7 cm? (a) Yes (b) No
  24. 24.In triangle ABC, angle A = 84° and angle B = 23°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 6 cm, 9 cm and 5 cm? (a) Yes (b) No
  28. 28.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)?
  29. 29.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 94° and angle B = 64°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 38° and angle B = 51°. What is angle C (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 36° and 54°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  35. 35.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  36. 36.In triangle ABC, angle A = 98° and angle B = 32°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 25° and angle B = 32°. What is angle C (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  40. 40.The two interior opposite angles of a triangle are 40° and 74°. What is the exterior angle (in degrees)?

Answer key

  1. 110
  2. 49
  3. 25
  4. Yes
  5. 4
  6. No
  7. 133
  8. No
  9. 90
  10. 70
  11. 40
  12. 20
  13. 49
  14. 85
  15. 36
  16. 71
  17. 43
  18. 36
  19. 5
  20. 33
  21. 45
  22. 84
  23. Yes
  24. 73
  25. 18
  26. 17
  27. Yes
  28. 24
  29. 51
  30. 22
  31. 91
  32. 90
  33. 74
  34. 12
  35. 18
  36. 50
  37. 27
  38. 123
  39. 5
  40. 114

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