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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 228 · 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 = 45° and angle B = 53°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  6. 6.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)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 77° and 59°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 77° and angle B = 69°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 31° and angle B = 24°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 5 cm, 7 cm and 7 cm? (a) No (b) Yes
  12. 12.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 5 cm, 11 cm and 5 cm? (a) Yes (b) No
  16. 16.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 4 cm and 5 cm? (a) Yes (b) No
  19. 19.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)?
  20. 20.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 73° and angle B = 74°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 13 cm, 7 cm and 12 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  28. 28.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 46° and 56°. What is the exterior angle (in degrees)?
  30. 30.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 73° and angle B = 40°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 73° and angle B = 51°. What is angle C (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  36. 36.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  37. 37.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  38. 38.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  39. 39.Can a triangle have sides of 16 cm, 12 cm and 2 cm? (a) No (b) Yes
  40. 40.Can a triangle have sides of 19 cm, 9 cm and 5 cm? (a) Yes (b) No

Answer key

  1. 82
  2. 40
  3. 124
  4. 26
  5. 22
  6. 6
  7. 70
  8. 136
  9. 34
  10. 125
  11. Yes
  12. 45
  13. 72
  14. 64
  15. No
  16. 72
  17. 61
  18. Yes
  19. 15
  20. 52
  21. 20
  22. 64
  23. 63
  24. 25
  25. 33
  26. Yes
  27. 70
  28. 5
  29. 102
  30. 59
  31. 67
  32. 22
  33. 56
  34. 17
  35. 54
  36. 3
  37. 20
  38. 8
  39. No
  40. No

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