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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 282 · 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 3 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 32° and angle B = 28°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  7. 7.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 44° and angle B = 112°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 38° and angle B = 90°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 26° and angle B = 49°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 27° and angle B = 41°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 69° and 77°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 81° and angle B = 40°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 5 cm, 9 cm and 8 cm? (a) Yes (b) No
  22. 22.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  23. 23.Can a triangle have sides of 8 cm, 6 cm and 9 cm? (a) Yes (b) No
  24. 24.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  25. 25.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)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  28. 28.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)?
  29. 29.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 40° and angle B = 85°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 24° and angle B = 33°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 78° and angle B = 67°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 39° and 63°. What is the exterior angle (in degrees)?

Answer key

  1. 45
  2. 120
  3. 27
  4. 61
  5. 56
  6. 17
  7. 31
  8. 24
  9. 68
  10. 18
  11. 100
  12. 52
  13. 105
  14. 112
  15. 20
  16. 79
  17. 36
  18. 90
  19. 146
  20. 59
  21. Yes
  22. 79
  23. Yes
  24. 16
  25. 8
  26. 80
  27. 40
  28. 7
  29. 82
  30. 55
  31. 123
  32. 35
  33. 38
  34. 84
  35. 43
  36. 70
  37. 34
  38. 12
  39. 36
  40. 102

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