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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 220 · 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 = 32° and angle B = 61°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 9 cm, 8 cm and 2 cm? (a) Yes (b) No
  4. 4.In triangle ABC, angle A = 38° and angle B = 103°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 9 cm, 9 cm and 2 cm? (a) No (b) Yes
  6. 6.The two interior opposite angles of a triangle are 20° and 37°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  9. 9.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)?
  10. 10.In triangle ABC, angle A = 30° and angle B = 47°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 63° and angle B = 56°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 75° and angle B = 54°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 2 cm and 11 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 83° and angle B = 73°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 27° and 44°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 27° and angle B = 46°. What is angle C (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 48° and 60°. What is the exterior angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 49° and angle B = 98°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 57° and 73°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 69° and 22°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 3 cm and 12 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 14 cm, 3 cm and 8 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 97° and angle B = 26°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 4 cm and 10 cm? (a) Yes (b) No

Answer key

  1. 87
  2. 42
  3. Yes
  4. 39
  5. Yes
  6. 57
  7. 74
  8. 39
  9. 8
  10. 103
  11. 90
  12. 48
  13. 104
  14. 61
  15. 90
  16. 36
  17. 51
  18. 90
  19. 78
  20. 59
  21. 34
  22. Yes
  23. 24
  24. 75
  25. 71
  26. 20
  27. 107
  28. 75
  29. 78
  30. 68
  31. 108
  32. 16
  33. 13
  34. 33
  35. 130
  36. 91
  37. Yes
  38. No
  39. 57
  40. Yes

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