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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 88 · 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 52° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  6. 6.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)?
  7. 7.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 25° and 66°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 57° and angle B = 39°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 7 cm, 8 cm and 12 cm? (a) No (b) Yes
  11. 11.Can a triangle have sides of 11 cm, 10 cm and 19 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 88° and angle B = 43°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 3 cm and 9 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 50° and angle B = 45°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 91° and angle B = 52°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 58° and angle B = 82°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  22. 22.Can a triangle have sides of 11 cm, 6 cm and 18 cm? (a) Yes (b) No
  23. 23.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  25. 25.Can a triangle have sides of 8 cm, 3 cm and 6 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 22° and 67°. What is the exterior angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  29. 29.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 89° and angle B = 46°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  36. 36.Can a triangle have sides of 21 cm, 9 cm and 8 cm? (a) Yes (b) No
  37. 37.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  38. 38.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 22° and angle B = 20°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 97° and angle B = 51°. What is angle C (in degrees)?

Answer key

  1. 76
  2. 46
  3. 84
  4. 15
  5. 25
  6. 7
  7. 18
  8. 91
  9. 84
  10. Yes
  11. Yes
  12. 49
  13. 19
  14. 100
  15. Yes
  16. 85
  17. 37
  18. 40
  19. 16
  20. 48
  21. 15
  22. No
  23. 13
  24. 50
  25. Yes
  26. 20
  27. 89
  28. 17
  29. 23
  30. 45
  31. 40
  32. 50
  33. No
  34. 60
  35. 40
  36. No
  37. 26
  38. 68
  39. 138
  40. 32

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