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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 492 · 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 37° each. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.Can a triangle have sides of 10 cm, 10 cm and 21 cm? (a) Yes (b) No
  6. 6.The two interior opposite angles of a triangle are 66° and 23°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 49°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 36° and angle B = 21°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 25° and 80°. What is the exterior angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  16. 16.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 22° and 48°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 4 cm, 11 cm and 2 cm? (a) Yes (b) No
  21. 21.The two interior opposite angles of a triangle are 53° and 37°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 27° and angle B = 100°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 3 cm and 12 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 45° and angle B = 84°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  32. 32.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)?
  33. 33.The two interior opposite angles of a triangle are 31° and 42°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 27° and 28°. What is the exterior angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 45° and angle B = 96°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 15 cm, 5 cm and 7 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?

Answer key

  1. 106
  2. 70
  3. 31
  4. 80
  5. No
  6. 89
  7. 21
  8. 76
  9. 27
  10. 90
  11. 17
  12. 26
  13. 123
  14. 105
  15. 25
  16. 15
  17. 69
  18. 37
  19. 70
  20. No
  21. 90
  22. 104
  23. 72
  24. 46
  25. 65
  26. 53
  27. Yes
  28. 51
  29. 36
  30. 30
  31. 30
  32. 9
  33. 73
  34. 55
  35. 13
  36. 20
  37. 48
  38. 39
  39. No
  40. 49

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