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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 334 · 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 83° each. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  5. 5.Can a triangle have sides of 10 cm, 11 cm and 7 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  8. 8.In triangle ABC, angle A = 33° and angle B = 79°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 24° and angle B = 92°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 28° and 75°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 7 cm, 22 cm and 10 cm? (a) Yes (b) No
  18. 18.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 50° and angle B = 30°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  21. 21.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)?
  22. 22.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  23. 23.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)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.Can a triangle have sides of 10 cm, 20 cm and 10 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  28. 28.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)?
  29. 29.Can a triangle have sides of 5 cm, 12 cm and 22 cm? (a) No (b) Yes
  30. 30.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 78° and angle B = 24°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  38. 38.Can a triangle have sides of 22 cm, 9 cm and 9 cm? (a) No (b) Yes
  39. 39.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)?
  40. 40.In triangle ABC, angle A = 97° and angle B = 61°. What is angle C (in degrees)?

Answer key

  1. 14
  2. 52
  3. 16
  4. 26
  5. Yes
  6. 30
  7. 40
  8. 68
  9. 76
  10. 72
  11. 20
  12. 13
  13. 64
  14. 77
  15. 103
  16. 104
  17. No
  18. 90
  19. 100
  20. 36
  21. 12
  22. 100
  23. 5
  24. 25
  25. No
  26. 67
  27. 84
  28. 8
  29. No
  30. 54
  31. 31
  32. 57
  33. 90
  34. 60
  35. 25
  36. 78
  37. 33
  38. No
  39. 24
  40. 22

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