A simple problem from 3d math primer book

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The question



A man is boarding a plane. The airline has a rule that no carry-on item may
be more than two feet long, two feet wide, or two feet tall. He has a very
valuable sword that is three feet long, yet he is able to carry the sword
on board with him.9 How is he able to do this? What is the longest possible
item that he could carry on?


And the answer is



The man buys a box or has a piece of luggage that is 2 feet long, 2 feet
wide, and 2 feet tall. If the object is very thin, such as a sword, then he
can put the object diagonally in the box or luggage. The longest such
object he could carry on is


$sqrt2^2 + 2^2 + 2^2$ ≈ 3.46 feet



What i don't understand is how the maximum object length is 3.46 feet. we can imagine a box then length of diagonal by Pythagorus theorem is $sqrt2^2 + 2^2$ ≈ 2.8284271 feet. why did the author took extra $2^2$.







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    The question



    A man is boarding a plane. The airline has a rule that no carry-on item may
    be more than two feet long, two feet wide, or two feet tall. He has a very
    valuable sword that is three feet long, yet he is able to carry the sword
    on board with him.9 How is he able to do this? What is the longest possible
    item that he could carry on?


    And the answer is



    The man buys a box or has a piece of luggage that is 2 feet long, 2 feet
    wide, and 2 feet tall. If the object is very thin, such as a sword, then he
    can put the object diagonally in the box or luggage. The longest such
    object he could carry on is


    $sqrt2^2 + 2^2 + 2^2$ ≈ 3.46 feet



    What i don't understand is how the maximum object length is 3.46 feet. we can imagine a box then length of diagonal by Pythagorus theorem is $sqrt2^2 + 2^2$ ≈ 2.8284271 feet. why did the author took extra $2^2$.







    share|cite|improve this question





















      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      The question



      A man is boarding a plane. The airline has a rule that no carry-on item may
      be more than two feet long, two feet wide, or two feet tall. He has a very
      valuable sword that is three feet long, yet he is able to carry the sword
      on board with him.9 How is he able to do this? What is the longest possible
      item that he could carry on?


      And the answer is



      The man buys a box or has a piece of luggage that is 2 feet long, 2 feet
      wide, and 2 feet tall. If the object is very thin, such as a sword, then he
      can put the object diagonally in the box or luggage. The longest such
      object he could carry on is


      $sqrt2^2 + 2^2 + 2^2$ ≈ 3.46 feet



      What i don't understand is how the maximum object length is 3.46 feet. we can imagine a box then length of diagonal by Pythagorus theorem is $sqrt2^2 + 2^2$ ≈ 2.8284271 feet. why did the author took extra $2^2$.







      share|cite|improve this question











      The question



      A man is boarding a plane. The airline has a rule that no carry-on item may
      be more than two feet long, two feet wide, or two feet tall. He has a very
      valuable sword that is three feet long, yet he is able to carry the sword
      on board with him.9 How is he able to do this? What is the longest possible
      item that he could carry on?


      And the answer is



      The man buys a box or has a piece of luggage that is 2 feet long, 2 feet
      wide, and 2 feet tall. If the object is very thin, such as a sword, then he
      can put the object diagonally in the box or luggage. The longest such
      object he could carry on is


      $sqrt2^2 + 2^2 + 2^2$ ≈ 3.46 feet



      What i don't understand is how the maximum object length is 3.46 feet. we can imagine a box then length of diagonal by Pythagorus theorem is $sqrt2^2 + 2^2$ ≈ 2.8284271 feet. why did the author took extra $2^2$.









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      asked Aug 3 at 6:18









      Atul

      1106




      1106




















          1 Answer
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          You are only thinking 2D, not 3D.



          That $2.82$ number is the length of the diagonal along the box's bottom. Run along that diagonal and then up two feet along one of the boxes vertical corner edges to make another right triangle whose hypotenuse length is $$sqrt(2.82ldots)^2+2^2=3.46ldots$$ Since the $2.82ldots$ came from $sqrt2^2+2^2$, it's the same as $$sqrt2^2+2^2+2^2=3.46ldots$$






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          • 1




            so one side of sword is touching the bottom corner of the box and other side is touching the opposite top corner of the box. right.
            – Atul
            Aug 3 at 6:27










          Your Answer




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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          1
          down vote



          accepted










          You are only thinking 2D, not 3D.



          That $2.82$ number is the length of the diagonal along the box's bottom. Run along that diagonal and then up two feet along one of the boxes vertical corner edges to make another right triangle whose hypotenuse length is $$sqrt(2.82ldots)^2+2^2=3.46ldots$$ Since the $2.82ldots$ came from $sqrt2^2+2^2$, it's the same as $$sqrt2^2+2^2+2^2=3.46ldots$$






          share|cite|improve this answer

















          • 1




            so one side of sword is touching the bottom corner of the box and other side is touching the opposite top corner of the box. right.
            – Atul
            Aug 3 at 6:27














          up vote
          1
          down vote



          accepted










          You are only thinking 2D, not 3D.



          That $2.82$ number is the length of the diagonal along the box's bottom. Run along that diagonal and then up two feet along one of the boxes vertical corner edges to make another right triangle whose hypotenuse length is $$sqrt(2.82ldots)^2+2^2=3.46ldots$$ Since the $2.82ldots$ came from $sqrt2^2+2^2$, it's the same as $$sqrt2^2+2^2+2^2=3.46ldots$$






          share|cite|improve this answer

















          • 1




            so one side of sword is touching the bottom corner of the box and other side is touching the opposite top corner of the box. right.
            – Atul
            Aug 3 at 6:27












          up vote
          1
          down vote



          accepted







          up vote
          1
          down vote



          accepted






          You are only thinking 2D, not 3D.



          That $2.82$ number is the length of the diagonal along the box's bottom. Run along that diagonal and then up two feet along one of the boxes vertical corner edges to make another right triangle whose hypotenuse length is $$sqrt(2.82ldots)^2+2^2=3.46ldots$$ Since the $2.82ldots$ came from $sqrt2^2+2^2$, it's the same as $$sqrt2^2+2^2+2^2=3.46ldots$$






          share|cite|improve this answer













          You are only thinking 2D, not 3D.



          That $2.82$ number is the length of the diagonal along the box's bottom. Run along that diagonal and then up two feet along one of the boxes vertical corner edges to make another right triangle whose hypotenuse length is $$sqrt(2.82ldots)^2+2^2=3.46ldots$$ Since the $2.82ldots$ came from $sqrt2^2+2^2$, it's the same as $$sqrt2^2+2^2+2^2=3.46ldots$$







          share|cite|improve this answer













          share|cite|improve this answer



          share|cite|improve this answer











          answered Aug 3 at 6:22









          alex.jordan

          36.9k459117




          36.9k459117







          • 1




            so one side of sword is touching the bottom corner of the box and other side is touching the opposite top corner of the box. right.
            – Atul
            Aug 3 at 6:27












          • 1




            so one side of sword is touching the bottom corner of the box and other side is touching the opposite top corner of the box. right.
            – Atul
            Aug 3 at 6:27







          1




          1




          so one side of sword is touching the bottom corner of the box and other side is touching the opposite top corner of the box. right.
          – Atul
          Aug 3 at 6:27




          so one side of sword is touching the bottom corner of the box and other side is touching the opposite top corner of the box. right.
          – Atul
          Aug 3 at 6:27












           

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