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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 610 · 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 3 cm, 3 cm and 10 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 6 cm, 12 cm and 10 cm? (a) No (b) Yes
  4. 4.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 8 cm, 19 cm and 9 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 79° and 66°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 47° and angle B = 65°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 7 cm, 8 cm and 11 cm? (a) No (b) Yes
  14. 14.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 65° and angle B = 41°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  18. 18.Can a triangle have sides of 5 cm, 7 cm and 7 cm? (a) No (b) Yes
  19. 19.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 33° and angle B = 114°. What is angle C (in degrees)?
  25. 25.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  26. 26.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.Can a triangle have sides of 14 cm, 12 cm and 7 cm? (a) No (b) Yes
  29. 29.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 31° and angle B = 26°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 39° and angle B = 94°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 63° and angle B = 96°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 6 cm, 5 cm and 9 cm? (a) No (b) Yes
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 6 cm and 3 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 13 cm and 4 cm? (a) No (b) Yes

Answer key

  1. 72
  2. No
  3. Yes
  4. 33
  5. No
  6. 21
  7. 36
  8. 145
  9. 68
  10. 26
  11. 15
  12. 77
  13. Yes
  14. 18
  15. 74
  16. 61
  17. 20
  18. Yes
  19. 13
  20. 52
  21. 46
  22. 41
  23. 30
  24. 33
  25. 18
  26. 72
  27. 25
  28. Yes
  29. 37
  30. 123
  31. 47
  32. 52
  33. 21
  34. 86
  35. Yes
  36. 39
  37. 100
  38. Yes
  39. 74
  40. Yes

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