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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 970 · 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 a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 25° and angle B = 29°. What is angle C (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 38° and angle B = 106°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 7 cm, 15 cm and 3 cm? (a) No (b) Yes
  8. 8.Can a triangle have sides of 11 cm, 3 cm and 19 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 98° and angle B = 50°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 67° and angle B = 71°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 27 cm, 10 cm and 12 cm? (a) No (b) Yes
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  16. 16.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 5 cm, 8 cm and 4 cm? (a) No (b) Yes
  19. 19.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)?
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  22. 22.In triangle ABC, angle A = 40° and angle B = 83°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  26. 26.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)?
  27. 27.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 75° and 32°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 4 cm, 10 cm and 10 cm? (a) No (b) Yes
  33. 33.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 20° and 50°. What is the exterior angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 6 cm and 9 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 31° and angle B = 42°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 89° and angle B = 38°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 24° and angle B = 55°. What is angle C (in degrees)?

Answer key

  1. 71
  2. 54
  3. 114
  4. 126
  5. 10
  6. 36
  7. No
  8. No
  9. 32
  10. 42
  11. No
  12. 120
  13. 50
  14. 48
  15. 25
  16. 24
  17. 34
  18. Yes
  19. 7
  20. 40
  21. 63
  22. 57
  23. 44
  24. 84
  25. 48
  26. 24
  27. 68
  28. 48
  29. 107
  30. 74
  31. 14
  32. Yes
  33. 4
  34. 70
  35. 25
  36. 46
  37. No
  38. 107
  39. 53
  40. 101

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