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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 515 · 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 39° each. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 52° and 31°. What is the exterior angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  6. 6.Can a triangle have sides of 10 cm, 7 cm and 10 cm? (a) Yes (b) No
  7. 7.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 18 cm, 7 cm and 7 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 47° and angle B = 37°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 77° and angle B = 20°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 20° and 33°. What is the exterior angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 72° and angle B = 43°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 30° and angle B = 66°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.The two interior opposite angles of a triangle are 20° and 69°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 7 cm, 2 cm and 6 cm? (a) No (b) Yes
  30. 30.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 76° and angle B = 52°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 22 cm and 12 cm? (a) Yes (b) No
  33. 33.Can a triangle have sides of 5 cm, 3 cm and 3 cm? (a) Yes (b) No
  34. 34.Can a triangle have sides of 10 cm, 5 cm and 16 cm? (a) Yes (b) No
  35. 35.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 40° and 71°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 24° and angle B = 55°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 12 cm, 6 cm and 21 cm? (a) No (b) Yes

Answer key

  1. 102
  2. 64
  3. 83
  4. 52
  5. 26
  6. Yes
  7. 13
  8. 11
  9. 29
  10. 45
  11. 90
  12. No
  13. 24
  14. 36
  15. 54
  16. 25
  17. 12
  18. 78
  19. 96
  20. 83
  21. 72
  22. 53
  23. 70
  24. 65
  25. 84
  26. 5
  27. 89
  28. 73
  29. Yes
  30. 74
  31. 52
  32. No
  33. Yes
  34. No
  35. 23
  36. 48
  37. 120
  38. 111
  39. 101
  40. No

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