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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 11 · 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 18°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 2 cm and 8 cm? (a) No (b) Yes
  3. 3.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 10 cm, 21 cm and 11 cm? (a) Yes (b) No
  5. 5.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  8. 8.Can a triangle have sides of 10 cm, 21 cm and 9 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 16 cm and 10 cm? (a) No (b) Yes
  14. 14.In triangle ABC, angle A = 86° and angle B = 29°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 20° and angle B = 36°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 147°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 22 cm, 11 cm and 7 cm? (a) Yes (b) No
  20. 20.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 14 cm, 9 cm and 2 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  27. 27.In triangle ABC, angle A = 43° and angle B = 75°. What is angle C (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 77° and angle B = 72°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 29° and angle B = 111°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 16 cm and 5 cm? (a) Yes (b) No
  36. 36.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  37. 37.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  38. 38.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?

Answer key

  1. 72
  2. Yes
  3. 13
  4. No
  5. 57
  6. 66
  7. 25
  8. No
  9. 18
  10. 22
  11. 45
  12. 116
  13. No
  14. 65
  15. 136
  16. 13
  17. 124
  18. 76
  19. No
  20. 30
  21. 42
  22. 84
  23. 61
  24. No
  25. 21
  26. 31
  27. 62
  28. 36
  29. 25
  30. 20
  31. 45
  32. 60
  33. 31
  34. 40
  35. No
  36. 5
  37. 26
  38. 100
  39. 60
  40. 17

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