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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 498 · 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 = 69° and angle B = 65°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 57° and 38°. What is the exterior angle (in degrees)?
  5. 5.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)?
  6. 6.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  10. 10.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)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 50° and angle B = 88°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  14. 14.Can a triangle have sides of 9 cm, 15 cm and 5 cm? (a) Yes (b) No
  15. 15.The two interior opposite angles of a triangle are 22° and 23°. What is the exterior angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 17 cm, 7 cm and 9 cm? (a) Yes (b) No
  18. 18.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  20. 20.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 57° and angle B = 47°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 70° and angle B = 82°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  31. 31.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  32. 32.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 60° and 31°. What is the exterior angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 52° and angle B = 54°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 6 cm, 16 cm and 6 cm? (a) No (b) Yes
  40. 40.In triangle ABC, angle A = 34° and angle B = 110°. What is angle C (in degrees)?

Answer key

  1. 46
  2. 44
  3. 54
  4. 95
  5. 12
  6. 80
  7. 30
  8. 25
  9. 22
  10. 8
  11. 77
  12. 42
  13. 72
  14. No
  15. 45
  16. 18
  17. No
  18. 42
  19. 17
  20. 29
  21. 70
  22. 47
  23. 76
  24. 54
  25. 38
  26. 28
  27. 21
  28. 57
  29. 75
  30. 17
  31. 4
  32. 36
  33. 39
  34. 91
  35. 30
  36. 40
  37. 74
  38. 66
  39. No
  40. 36

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