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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 976 · 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 45°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  5. 5.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)?
  6. 6.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (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 = 32° and angle B = 96°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  12. 12.An exterior angle of a triangle is 43°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  16. 16.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)?
  17. 17.Can a triangle have sides of 11 cm, 7 cm and 19 cm? (a) Yes (b) No
  18. 18.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 30° and angle B = 44°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  21. 21.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 77° and angle B = 79°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 21° and 69°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 94° and angle B = 28°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 85° and angle B = 51°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 20° and angle B = 124°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 60° and angle B = 58°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 60° and angle B = 99°. What is angle C (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.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 2 cm, 12 cm and 13 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 33° and 57°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 57° and 35°. What is the exterior angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 54° and angle B = 75°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 12 cm, 8 cm and 20 cm? (a) Yes (b) No

Answer key

  1. 45
  2. 22
  3. 20
  4. 80
  5. 16
  6. 138
  7. 40
  8. 52
  9. 36
  10. 36
  11. 18
  12. 20
  13. 5
  14. 28
  15. 25
  16. 15
  17. No
  18. 34
  19. 106
  20. 25
  21. 108
  22. 57
  23. 24
  24. 90
  25. 58
  26. 78
  27. 44
  28. 36
  29. 62
  30. 46
  31. 21
  32. 17
  33. 72
  34. Yes
  35. 90
  36. 16
  37. 92
  38. 39
  39. 51
  40. No

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