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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 681 · 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 12 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 46° and 37°. What is the exterior angle (in degrees)?
  4. 4.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  5. 5.In triangle ABC, angle A = 97° and angle B = 38°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  10. 10.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 10 cm, 5 cm and 12 cm? (a) Yes (b) No
  13. 13.In triangle ABC, angle A = 35° and angle B = 120°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 49° and 41°. What is the exterior angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  17. 17.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  18. 18.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 40° and angle B = 86°. What is angle C (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 26° and 50°. What is the exterior angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 12 cm, 13 cm and 5 cm? (a) No (b) Yes
  25. 25.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) No (b) Yes
  26. 26.The two interior opposite angles of a triangle are 80° and 68°. What is the exterior angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  28. 28.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 50° and angle B = 95°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  34. 34.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 60° and angle B = 52°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 48° and 42°. What is the exterior angle (in degrees)?

Answer key

  1. No
  2. 19
  3. 83
  4. 12
  5. 45
  6. 14
  7. 72
  8. 23
  9. 15
  10. 25
  11. 72
  12. Yes
  13. 25
  14. 90
  15. 36
  16. 53
  17. 15
  18. 13
  19. 20
  20. 54
  21. 13
  22. 76
  23. 17
  24. Yes
  25. No
  26. 148
  27. 5
  28. 25
  29. 69
  30. 35
  31. 11
  32. 33
  33. 70
  34. 55
  35. 32
  36. 68
  37. 84
  38. 138
  39. 63
  40. 90

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