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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 708 · 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.

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  1. 1.In triangle ABC, angle A = 64° and angle B = 69°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 27° and angle B = 123°. What is angle C (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 53° and 40°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) Yes (b) No
  7. 7.In triangle ABC, angle A = 43° and angle B = 57°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 63° and angle B = 44°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 78° and 23°. What is the exterior angle (in degrees)?
  11. 11.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)?
  12. 12.Can a triangle have sides of 7 cm, 20 cm and 10 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 34° and angle B = 22°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 19 cm, 8 cm and 8 cm? (a) Yes (b) No
  17. 17.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  18. 18.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)?
  19. 19.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  20. 20.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 73° and angle B = 37°. What is angle C (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 74° and 43°. What is the exterior angle (in degrees)?
  23. 23.Can a triangle have sides of 7 cm, 3 cm and 8 cm? (a) No (b) Yes
  24. 24.Can a triangle have sides of 8 cm, 9 cm and 21 cm? (a) Yes (b) No
  25. 25.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 23° and angle B = 40°. What is angle C (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 80° and angle B = 56°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 69° and 28°. What is the exterior angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  32. 32.The two interior opposite angles of a triangle are 61° and 32°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 7 cm and 12 cm? (a) No (b) Yes
  35. 35.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?

Answer key

  1. 47
  2. 52
  3. 78
  4. 30
  5. 93
  6. No
  7. 80
  8. 73
  9. 72
  10. 101
  11. 24
  12. No
  13. 94
  14. 50
  15. 124
  16. No
  17. 25
  18. 8
  19. 46
  20. 62
  21. 70
  22. 117
  23. Yes
  24. No
  25. 70
  26. 117
  27. 36
  28. 44
  29. 74
  30. 97
  31. 20
  32. 93
  33. 75
  34. Yes
  35. 75
  36. 79
  37. 60
  38. 72
  39. 11
  40. 45

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