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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 797 · 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 an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 50° and angle B = 38°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 56° and angle B = 87°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 71° and angle B = 48°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 58° and angle B = 21°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 22° and angle B = 71°. What is angle C (in degrees)?
  14. 14.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  20. 20.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  21. 21.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 39° and angle B = 38°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 42° and angle B = 39°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 26° and 42°. What is the exterior angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 78° and 23°. What is the exterior angle (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 40° and angle B = 99°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 9 cm and 15 cm? (a) No (b) Yes
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 51° and angle B = 23°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 10 cm, 24 cm and 12 cm? (a) No (b) Yes
  35. 35.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 21° and 49°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 6 cm, 6 cm and 16 cm? (a) Yes (b) No
  38. 38.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)?
  39. 39.Can a triangle have sides of 11 cm, 23 cm and 10 cm? (a) No (b) Yes
  40. 40.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?

Answer key

  1. 47
  2. 61
  3. 92
  4. 57
  5. 25
  6. 37
  7. 40
  8. 61
  9. 90
  10. 47
  11. 101
  12. 58
  13. 87
  14. 25
  15. 48
  16. 63
  17. 32
  18. 80
  19. 45
  20. 24
  21. 42
  22. 103
  23. 99
  24. 68
  25. 50
  26. 101
  27. 12
  28. 41
  29. 54
  30. Yes
  31. 72
  32. 17
  33. 106
  34. No
  35. 48
  36. 70
  37. No
  38. 15
  39. No
  40. 26

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