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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 238 · 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 = 24° and angle B = 106°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 69° and angle B = 30°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  5. 5.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 56° and 77°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 65° and angle B = 49°. What is angle C (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 41° and angle B = 35°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 21° and 46°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 8 cm and 10 cm? (a) Yes (b) No
  17. 17.Can a triangle have sides of 10 cm, 9 cm and 11 cm? (a) Yes (b) No
  18. 18.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 96° and angle B = 28°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 8 cm, 14 cm and 3 cm? (a) Yes (b) No
  23. 23.The two interior opposite angles of a triangle are 52° and 51°. What is the exterior angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 25° and 68°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 84° and angle B = 30°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 59° and angle B = 73°. What is angle C (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.Can a triangle have sides of 10 cm, 16 cm and 5 cm? (a) No (b) Yes
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 42° and angle B = 58°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  34. 34.Can a triangle have sides of 10 cm, 11 cm and 2 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 67° and 46°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  39. 39.In triangle ABC, angle A = 96° and angle B = 54°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?

Answer key

  1. 50
  2. 30
  3. 81
  4. 5
  5. 45
  6. 133
  7. 66
  8. 25
  9. 104
  10. 52
  11. 72
  12. 20
  13. 20
  14. 90
  15. 67
  16. Yes
  17. Yes
  18. 112
  19. 43
  20. 25
  21. 56
  22. No
  23. 103
  24. 93
  25. 66
  26. 79
  27. 48
  28. 7
  29. No
  30. 72
  31. 80
  32. 30
  33. 9
  34. Yes
  35. 113
  36. 48
  37. 40
  38. 12
  39. 30
  40. 57

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