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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 333 · 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.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  4. 4.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  6. 6.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)?
  7. 7.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  12. 12.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  13. 13.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  17. 17.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  18. 18.In triangle ABC, angle A = 25° and angle B = 75°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 40° and 31°. What is the exterior angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 9 cm, 6 cm and 3 cm? (a) No (b) Yes
  25. 25.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 9 cm, 17 cm and 4 cm? (a) Yes (b) No
  28. 28.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  29. 29.In triangle ABC, angle A = 71° and angle B = 75°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 7 cm and 20 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 91° and angle B = 25°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  36. 36.Can a triangle have sides of 14 cm, 12 cm and 3 cm? (a) No (b) Yes
  37. 37.The two interior opposite angles of a triangle are 50° and 27°. What is the exterior angle (in degrees)?
  38. 38.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 72° and angle B = 22°. What is angle C (in degrees)?

Answer key

  1. 32
  2. 120
  3. 26
  4. 45
  5. 36
  6. 16
  7. 18
  8. 24
  9. 33
  10. 79
  11. 32
  12. 48
  13. 41
  14. 56
  15. 52
  16. 27
  17. 7
  18. 80
  19. 130
  20. 20
  21. 20
  22. 71
  23. 13
  24. No
  25. 36
  26. 75
  27. No
  28. 30
  29. 34
  30. No
  31. 49
  32. 64
  33. 41
  34. 39
  35. 5
  36. Yes
  37. 77
  38. 36
  39. 45
  40. 86

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