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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 302 · 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 38°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 15°. 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.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  6. 6.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 81° and angle B = 75°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 6 cm, 11 cm and 6 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 81° and angle B = 41°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 7 cm, 3 cm and 6 cm? (a) No (b) Yes
  13. 13.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 10 cm, 10 cm and 17 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.In triangle ABC, angle A = 33° and angle B = 87°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  23. 23.Can a triangle have sides of 2 cm, 3 cm and 4 cm? (a) Yes (b) No
  24. 24.In triangle ABC, angle A = 40° and angle B = 108°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 67° and angle B = 75°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 56° and angle B = 76°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  35. 35.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)?
  36. 36.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 63° and angle B = 30°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 12 cm, 9 cm and 6 cm? (a) Yes (b) No

Answer key

  1. 52
  2. 25
  3. 75
  4. 100
  5. 20
  6. 72
  7. 72
  8. 24
  9. Yes
  10. 65
  11. 58
  12. Yes
  13. 84
  14. 60
  15. 21
  16. Yes
  17. 42
  18. 26
  19. 20
  20. 60
  21. 16
  22. 70
  23. Yes
  24. 32
  25. 45
  26. 38
  27. 50
  28. 61
  29. 40
  30. 72
  31. 48
  32. 36
  33. 28
  34. 20
  35. 12
  36. 36
  37. 48
  38. 30
  39. 87
  40. Yes

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