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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 191 · 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 two interior opposite angles of a triangle are 20° and 29°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 78° and angle B = 57°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.Can a triangle have sides of 10 cm, 9 cm and 11 cm? (a) No (b) Yes
  7. 7.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  9. 9.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)?
  10. 10.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 94° and angle B = 46°. What is angle C (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  13. 13.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  15. 15.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)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 12 cm, 4 cm and 21 cm? (a) Yes (b) No
  20. 20.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 19 cm, 7 cm and 8 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 20° and angle B = 103°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 10 cm, 8 cm and 14 cm? (a) No (b) Yes
  24. 24.The two interior opposite angles of a triangle are 46° and 49°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 25° and angle B = 52°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 26° and 27°. What is the exterior angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 23° and 68°. What is the exterior angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  32. 32.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)?
  33. 33.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 25° and 36°. What is the exterior angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 12 cm, 16 cm and 4 cm? (a) Yes (b) No
  38. 38.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)?
  39. 39.In triangle ABC, angle A = 68° and angle B = 56°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 20° and angle B = 43°. What is angle C (in degrees)?

Answer key

  1. 49
  2. 80
  3. 45
  4. 32
  5. 17
  6. Yes
  7. 45
  8. 72
  9. 24
  10. 45
  11. 40
  12. 15
  13. 31
  14. 36
  15. 12
  16. 78
  17. 20
  18. 62
  19. No
  20. 30
  21. No
  22. 57
  23. Yes
  24. 95
  25. 103
  26. 40
  27. 53
  28. 91
  29. 63
  30. 17
  31. 90
  32. 7
  33. 55
  34. 61
  35. 11
  36. 56
  37. No
  38. 24
  39. 56
  40. 117

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