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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 560 · 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 angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  3. 3.In triangle ABC, angle A = 24° and angle B = 124°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 23° and 33°. What is the exterior angle (in degrees)?
  5. 5.In triangle ABC, angle A = 31° and angle B = 49°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 96° and angle B = 42°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  10. 10.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)?
  11. 11.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (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.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  14. 14.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 6 cm, 3 cm and 8 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 87° and angle B = 45°. What is angle C (in degrees)?
  20. 20.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  21. 21.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 89° and angle B = 43°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 50° and angle B = 48°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  26. 26.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  27. 27.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 32° and angle B = 46°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.Can a triangle have sides of 17 cm, 12 cm and 4 cm? (a) Yes (b) No
  33. 33.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 7 cm and 11 cm? (a) Yes (b) No
  36. 36.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  38. 38.In triangle ABC, angle A = 56° and angle B = 94°. What is angle C (in degrees)?
  39. 39.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)?
  40. 40.In triangle ABC, angle A = 23° and angle B = 92°. What is angle C (in degrees)?

Answer key

  1. 45
  2. 25
  3. 32
  4. 56
  5. 100
  6. 63
  7. 116
  8. 42
  9. 122
  10. 4
  11. 70
  12. 12
  13. 23
  14. 48
  15. 71
  16. 56
  17. 75
  18. Yes
  19. 48
  20. 6
  21. 126
  22. 48
  23. 20
  24. 82
  25. 25
  26. 12
  27. 65
  28. 42
  29. 102
  30. 36
  31. 36
  32. No
  33. 67
  34. 68
  35. Yes
  36. 63
  37. 17
  38. 30
  39. 15
  40. 65

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