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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 476 · 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 a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  4. 4.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 23° and angle B = 73°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 90° and angle B = 67°. What is angle C (in degrees)?
  8. 8.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  9. 9.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  11. 11.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  12. 12.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  13. 13.Can a triangle have sides of 4 cm, 7 cm and 5 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 11 cm, 5 cm and 8 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 68° and angle B = 87°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  21. 21.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 39° and angle B = 46°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 89° and angle B = 32°. What is angle C (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 29° and 67°. What is the exterior angle (in degrees)?
  26. 26.Can a triangle have sides of 5 cm, 6 cm and 13 cm? (a) Yes (b) No
  27. 27.The two interior opposite angles of a triangle are 63° and 55°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 65° and 27°. What is the exterior angle (in degrees)?
  30. 30.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)?
  31. 31.The two interior opposite angles of a triangle are 37° and 59°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 92° and angle B = 62°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 53° and 57°. What is the exterior angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 61° and 30°. What is the exterior angle (in degrees)?
  37. 37.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)?
  38. 38.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?

Answer key

  1. 20
  2. 34
  3. 64
  4. 43
  5. 84
  6. 45
  7. 23
  8. 15
  9. 26
  10. 29
  11. 7
  12. 70
  13. Yes
  14. 57
  15. Yes
  16. 27
  17. 40
  18. 39
  19. 25
  20. 41
  21. 43
  22. 25
  23. 95
  24. 59
  25. 96
  26. No
  27. 118
  28. 43
  29. 92
  30. 12
  31. 96
  32. 26
  33. 110
  34. 90
  35. 66
  36. 91
  37. 15
  38. 66
  39. 46
  40. 29

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