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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 550 · 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.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 11 cm and 10 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 10 cm, 19 cm and 6 cm? (a) Yes (b) No
  4. 4.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 55° and angle B = 69°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 74° and angle B = 60°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 9 cm, 13 cm and 9 cm? (a) No (b) Yes
  12. 12.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 20° and 25°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 42° and angle B = 57°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 67° and angle B = 27°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 26° and 62°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 46° and angle B = 23°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 81° and angle B = 63°. What is angle C (in degrees)?
  29. 29.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 24° and 60°. What is the exterior angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  35. 35.In triangle ABC, angle A = 31° and angle B = 26°. What is angle C (in degrees)?
  36. 36.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)?
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  38. 38.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 70° and angle B = 28°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 9 cm and 3 cm? (a) Yes (b) No

Answer key

  1. 90
  2. Yes
  3. No
  4. 90
  5. 56
  6. 46
  7. 57
  8. 42
  9. 13
  10. 26
  11. Yes
  12. 30
  13. 15
  14. 45
  15. 72
  16. 81
  17. 70
  18. 114
  19. 70
  20. 47
  21. 86
  22. 56
  23. 88
  24. 36
  25. 134
  26. 27
  27. 111
  28. 36
  29. 6
  30. 36
  31. 15
  32. 79
  33. 84
  34. 17
  35. 123
  36. 5
  37. 10
  38. 13
  39. 82
  40. Yes

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