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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 754 · 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.Can a triangle have sides of 19 cm, 6 cm and 10 cm? (a) No (b) Yes
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.Can a triangle have sides of 10 cm, 21 cm and 7 cm? (a) Yes (b) No
  4. 4.In triangle ABC, angle A = 36° and angle B = 81°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 56° and 55°. What is the exterior angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 65° and 65°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 35° each. What is the third 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.The two interior opposite angles of a triangle are 20° and 77°. What is the exterior angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 57° and angle B = 35°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  19. 19.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  20. 20.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  22. 22.Can a triangle have sides of 9 cm, 11 cm and 4 cm? (a) Yes (b) No
  23. 23.Can a triangle have sides of 15 cm, 5 cm and 8 cm? (a) No (b) Yes
  24. 24.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 61° and 33°. What is the exterior angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  27. 27.The two interior opposite angles of a triangle are 66° and 77°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 3 cm, 3 cm and 2 cm? (a) No (b) Yes
  29. 29.The two interior opposite angles of a triangle are 78° and 21°. What is the exterior angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 30° and angle B = 50°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 6 cm, 2 cm and 5 cm? (a) No (b) Yes
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.The two interior opposite angles of a triangle are 70° and 69°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 62° and angle B = 57°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 38° and 61°. What is the exterior angle (in degrees)?

Answer key

  1. No
  2. 80
  3. No
  4. 63
  5. 32
  6. 18
  7. 88
  8. 111
  9. 130
  10. 110
  11. 100
  12. 97
  13. 26
  14. 45
  15. 88
  16. 58
  17. 120
  18. 8
  19. 3
  20. 61
  21. 17
  22. Yes
  23. No
  24. 42
  25. 94
  26. 15
  27. 143
  28. Yes
  29. 99
  30. 24
  31. 69
  32. 100
  33. 78
  34. 30
  35. 70
  36. Yes
  37. 17
  38. 139
  39. 61
  40. 99

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