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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 487 · 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.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 25° and 43°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 19 cm, 11 cm and 6 cm? (a) Yes (b) No
  6. 6.In triangle ABC, angle A = 33° and angle B = 42°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 83° and angle B = 62°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 60° and angle B = 20°. What is angle C (in degrees)?
  12. 12.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)?
  13. 13.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)?
  14. 14.Can a triangle have sides of 12 cm, 10 cm and 5 cm? (a) No (b) Yes
  15. 15.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  17. 17.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  18. 18.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  20. 20.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  23. 23.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 10 cm and 7 cm? (a) No (b) Yes
  25. 25.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  26. 26.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  27. 27.In triangle ABC, angle A = 33° and angle B = 29°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  29. 29.Can a triangle have sides of 10 cm, 3 cm and 4 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 55° and angle B = 63°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 27° and 75°. What is the exterior angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  33. 33.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  34. 34.Can a triangle have sides of 23 cm, 7 cm and 12 cm? (a) No (b) Yes
  35. 35.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  37. 37.Can a triangle have sides of 8 cm, 9 cm and 12 cm? (a) No (b) Yes
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  40. 40.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?

Answer key

  1. 24
  2. 10
  3. 68
  4. 24
  5. No
  6. 105
  7. 70
  8. 120
  9. 45
  10. 35
  11. 100
  12. 12
  13. 15
  14. Yes
  15. 52
  16. 55
  17. 24
  18. 20
  19. 71
  20. 48
  21. 28
  22. 11
  23. 72
  24. Yes
  25. 41
  26. 48
  27. 118
  28. 70
  29. No
  30. 62
  31. 102
  32. 13
  33. 25
  34. No
  35. 90
  36. 90
  37. Yes
  38. 90
  39. 15
  40. 24

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