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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 397 · 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 = 99° and angle B = 40°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 76° and angle B = 54°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (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.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)?
  11. 11.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 39° and 61°. What is the exterior angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 48° and 20°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 20 cm, 10 cm and 5 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 60° and angle B = 74°. What is angle C (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  23. 23.Can a triangle have sides of 8 cm, 9 cm and 8 cm? (a) No (b) Yes
  24. 24.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 93° and angle B = 48°. What is angle C (in degrees)?
  27. 27.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)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 22° and angle B = 37°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  34. 34.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 90° and angle B = 65°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 3 cm, 7 cm and 3 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 16 cm, 4 cm and 12 cm? (a) Yes (b) No

Answer key

  1. 41
  2. 100
  3. 122
  4. 100
  5. 50
  6. 73
  7. 50
  8. 26
  9. 90
  10. 15
  11. 9
  12. 61
  13. 100
  14. 84
  15. 44
  16. 68
  17. 13
  18. 32
  19. No
  20. 46
  21. 20
  22. 36
  23. Yes
  24. 17
  25. 43
  26. 39
  27. 8
  28. 120
  29. 13
  30. 57
  31. 62
  32. 121
  33. 5
  34. 67
  35. 36
  36. 25
  37. 24
  38. No
  39. 30
  40. No

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