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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 223 · 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 = 48° and angle B = 98°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 37° and angle B = 62°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 67° and angle B = 37°. What is angle C (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 61° and angle B = 93°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 86° and angle B = 60°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  13. 13.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  14. 14.Can a triangle have sides of 22 cm, 10 cm and 12 cm? (a) Yes (b) No
  15. 15.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 14 cm, 7 cm and 7 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 73° and angle B = 32°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 91° and angle B = 25°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  23. 23.Can a triangle have sides of 7 cm, 5 cm and 5 cm? (a) Yes (b) No
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 77° and angle B = 61°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  29. 29.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 35° and 49°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 3 cm, 12 cm and 7 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 9 cm, 7 cm and 14 cm? (a) No (b) Yes
  35. 35.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 61° and 64°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  40. 40.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 34
  2. 40
  3. 17
  4. 13
  5. 81
  6. 29
  7. 76
  8. 30
  9. 100
  10. 26
  11. 34
  12. 29
  13. 4
  14. No
  15. 33
  16. No
  17. 41
  18. 75
  19. 32
  20. 100
  21. 64
  22. 22
  23. Yes
  24. 80
  25. 24
  26. 42
  27. 74
  28. 44
  29. 46
  30. 44
  31. 84
  32. 75
  33. No
  34. Yes
  35. 12
  36. 37
  37. 125
  38. 36
  39. 25
  40. 100

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