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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 22 · 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 24 cm, 11 cm and 8 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 6 cm and 19 cm? (a) Yes (b) No
  4. 4.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)?
  5. 5.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 60° and 48°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 79° and angle B = 77°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  15. 15.Can a triangle have sides of 13 cm, 4 cm and 9 cm? (a) Yes (b) No
  16. 16.Can a triangle have sides of 26 cm, 9 cm and 12 cm? (a) No (b) Yes
  17. 17.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  18. 18.The two interior opposite angles of a triangle are 32° and 55°. What is the exterior angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  22. 22.In triangle ABC, angle A = 24° and angle B = 71°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 8 cm, 11 cm and 6 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 2 cm, 11 cm and 16 cm? (a) Yes (b) No
  27. 27.Can a triangle have sides of 5 cm, 2 cm and 4 cm? (a) Yes (b) No
  28. 28.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 64° and 37°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 73° and 20°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 95° and angle B = 40°. What is angle C (in degrees)?
  33. 33.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)?
  34. 34.Can a triangle have sides of 8 cm, 18 cm and 9 cm? (a) Yes (b) No
  35. 35.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 56
  3. No
  4. 36
  5. 58
  6. 45
  7. 24
  8. 74
  9. 108
  10. 86
  11. 24
  12. 42
  13. 41
  14. 33
  15. No
  16. No
  17. 13
  18. 87
  19. 90
  20. 40
  21. 18
  22. 85
  23. 94
  24. Yes
  25. 59
  26. No
  27. Yes
  28. 34
  29. 101
  30. 93
  31. 28
  32. 45
  33. 8
  34. No
  35. 72
  36. 53
  37. 18
  38. 90
  39. 35
  40. 65

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