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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 912 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 12 cm, 8 cm and 11 cm? (a) Yes (b) No
  2. 2.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 18 cm, 7 cm and 6 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 65° and angle B = 65°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) No (b) Yes
  10. 10.The two interior opposite angles of a triangle are 66° and 32°. What is the exterior angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  14. 14.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)?
  15. 15.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 23° and angle B = 45°. What is angle C (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 39° and 39°. What is the exterior angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  19. 19.Can a triangle have sides of 8 cm, 9 cm and 11 cm? (a) No (b) Yes
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 25° and angle B = 20°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  26. 26.Can a triangle have sides of 12 cm, 19 cm and 4 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  29. 29.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 11 cm, 7 cm and 13 cm? (a) No (b) Yes
  32. 32.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  34. 34.In triangle ABC, angle A = 21° and angle B = 50°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 26° and 32°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 9 cm, 11 cm and 22 cm? (a) Yes (b) No
  38. 38.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?

Answer key

  1. Yes
  2. 72
  3. 98
  4. 75
  5. No
  6. 34
  7. 5
  8. 50
  9. No
  10. 98
  11. 11
  12. 43
  13. 15
  14. 3
  15. 60
  16. 112
  17. 78
  18. 18
  19. Yes
  20. 40
  21. 41
  22. 38
  23. 22
  24. 135
  25. 17
  26. No
  27. 12
  28. 29
  29. 26
  30. 43
  31. Yes
  32. 5
  33. 77
  34. 109
  35. 58
  36. 63
  37. No
  38. 33
  39. 30
  40. 46

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