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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 475 · 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 an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 74° and 36°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 29° and angle B = 75°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 14 cm, 11 cm and 9 cm? (a) Yes (b) No
  14. 14.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 37° and 56°. What is the exterior 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.Can a triangle have sides of 12 cm, 22 cm and 6 cm? (a) Yes (b) No
  18. 18.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 69° and angle B = 42°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 22° and angle B = 60°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 8 cm, 2 cm and 9 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 78° and angle B = 72°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.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)?
  31. 31.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 53° and angle B = 76°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 11 cm, 18 cm and 6 cm? (a) No (b) Yes
  35. 35.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 3 cm and 6 cm? (a) Yes (b) No
  40. 40.The two interior opposite angles of a triangle are 70° and 56°. What is the exterior angle (in degrees)?

Answer key

  1. 32
  2. 110
  3. 39
  4. 90
  5. 76
  6. 74
  7. 10
  8. 50
  9. 38
  10. 10
  11. 45
  12. 33
  13. Yes
  14. 72
  15. 93
  16. 56
  17. No
  18. 17
  19. 26
  20. 69
  21. 20
  22. 39
  23. 98
  24. Yes
  25. 30
  26. 70
  27. 14
  28. 124
  29. 54
  30. 24
  31. 80
  32. 51
  33. 67
  34. No
  35. 74
  36. 38
  37. 64
  38. 25
  39. No
  40. 126

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