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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 687 · 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.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 25° and 63°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 2 cm, 8 cm and 2 cm? (a) No (b) Yes
  5. 5.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 7 cm, 24 cm and 12 cm? (a) Yes (b) No
  8. 8.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 74° and angle B = 46°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 100° and angle B = 58°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 30° and 67°. What is the exterior angle (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 a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 83° and angle B = 72°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 8 cm and 22 cm? (a) No (b) Yes
  21. 21.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  22. 22.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)?
  23. 23.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 95° and angle B = 44°. What is angle C (in degrees)?
  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.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)?
  30. 30.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  33. 33.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 48° and 57°. What is the exterior angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  36. 36.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 52° and angle B = 100°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 25° and angle B = 71°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?

Answer key

  1. 25
  2. 88
  3. 40
  4. No
  5. 55
  6. 51
  7. No
  8. 72
  9. 26
  10. 10
  11. 60
  12. 25
  13. 22
  14. 97
  15. 36
  16. 77
  17. 26
  18. 68
  19. 25
  20. No
  21. 52
  22. 7
  23. 50
  24. 69
  25. 114
  26. 22
  27. 41
  28. 24
  29. 16
  30. 10
  31. 90
  32. 25
  33. 48
  34. 105
  35. 20
  36. 77
  37. 28
  38. 33
  39. 84
  40. 20

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