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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 923 · 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 = 90° and angle B = 40°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  4. 4.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  5. 5.Can a triangle have sides of 6 cm, 4 cm and 6 cm? (a) No (b) Yes
  6. 6.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  7. 7.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)?
  8. 8.In triangle ABC, angle A = 49° and angle B = 44°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 59° and 47°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 97° and angle B = 46°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 9 cm and 21 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  14. 14.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 98° and angle B = 39°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 8 cm, 19 cm and 9 cm? (a) No (b) Yes
  25. 25.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  28. 28.Can a triangle have sides of 8 cm, 10 cm and 18 cm? (a) No (b) Yes
  29. 29.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  30. 30.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 93° and angle B = 57°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 7 cm, 4 cm and 3 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 32° and angle B = 74°. What is angle C (in degrees)?

Answer key

  1. 50
  2. 80
  3. 13
  4. 20
  5. Yes
  6. 29
  7. 8
  8. 87
  9. 45
  10. 106
  11. 37
  12. No
  13. 94
  14. 12
  15. 54
  16. 30
  17. 30
  18. 50
  19. 43
  20. 39
  21. 73
  22. 45
  23. 64
  24. No
  25. 26
  26. 27
  27. 15
  28. No
  29. 17
  30. 32
  31. 65
  32. 30
  33. No
  34. 110
  35. 25
  36. 20
  37. 50
  38. 31
  39. 59
  40. 74

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