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RADAR
(@dougie)
5,000+ posts Member

Where'd the Square Go...

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Topic starter Posted : April 11, 2021 8:45 am
Brad Ott liked
Dave Lindell
(@dave-lindell)
1,000+ posts Supporter

Check the slope of the lines.

There is an angle point in the hypotenuse after rearrangement.

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Posted : April 11, 2021 9:33 am
holy cow
(@holy-cow)
20,000+ posts Member

OZ?

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Posted : April 11, 2021 9:41 am

Bill93
(@bill93)
5,000+ posts Member

Yep, he cheats by not having the pieces lay flat on the grid. In the first picture the slope of the left triangle is 3/8 = 0.375 but the top triangle is 2/5 = 0.4, and it the second picture they are reversed so the kink goes the other way.

Was that a Sam Loyd puzzle? I recall Martin Gardner writing about him decades ago. I don't recall that he cheated that way, though, in the puzzles I saw.

(What a memory I have! But then I forgot to eat breakfast this morning.)

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Posted : April 11, 2021 11:20 am
Bill93
(@bill93)
5,000+ posts Member
Posted by: @dave-lindell

Before AND after, in opposite directions.

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Posted : April 11, 2021 11:21 am
Dave Lindell
(@dave-lindell)
1,000+ posts Supporter

@bill93:  I have a really good memory too.  It's just short.

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Posted : April 11, 2021 12:29 pm
RADAR liked

holy cow
(@holy-cow)
20,000+ posts Member

I am famous for both sides of my memory.  On the one side I remember minute details from decades ago.  On the other I can't remember your name though we were classmates in school for six years.  It will come to me, but embarrassingly late.

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Posted : April 11, 2021 3:04 pm
JaRo
 JaRo
(@jaro)
1,000+ posts Member

@holy-cow

My Grandmother could remember the slightest detail of something that happened many many years ago but could not remember how many time she had told that story to the same person and that same day.

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Posted : April 11, 2021 6:14 pm
holy cow
(@holy-cow)
20,000+ posts Member

@jaro

I'm getting closer to that every time I drive by some place that I surveyed. "Yeah, we surveyed that place back in 1987.  Mid-March as I recall.  It rained all day but we stuck with it as the job had to be delivered two days later."

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Posted : April 11, 2021 6:30 pm

FairbanksLS
(@fairbanksls)
200+ posts Member

I can remember details about surveys I did decades ago.  I could not remember my wedding anniversary.  I'm happily divorced and happily still surveying.

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Posted : April 11, 2021 6:32 pm
BStrand
(@bstrand)
1,000+ posts Member

Looks like a teaching aid to demonstrate small differences in angles.

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Posted : April 11, 2021 6:49 pm
FL/GA
(@flga-2-2)
5,000+ posts Supporter

@dave-lindell

what was the question?

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Posted : April 12, 2021 5:44 am

Paul in PA
(@paul-in-pa)
5,000+ posts Member

The four figures do not form a triangle in either arrangement. Because they are close you believe him when he says they are triangles, but he is a liar. They first is a quadrilateral, the second is an eight sided figure.

Optical delusion.

Paul in PA

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Posted : April 12, 2021 7:07 am
Brad Ott liked
MathTeacher
(@mathteacher)
1,000+ posts Member

It actually didn't "go" anywhere. The presenter would have you believe that the smaller triangle's base = 5 units and its height = 2 units. But that's not true. While the base does equal 5, the height is 1.923076923 units, to 10 digits. The large triangle has base = 8 units, but its height is actually 3.076923077 units, again to 10 significant digits.

The two rectangular areas, where the purportedly missing piece is, actually have identical areas when the heights of the triangles are computed correctly. 1.923076923 * 8 = 3.076923077 * 5 within the limits of precision of a 12-digit calculator.

So, the "missing piece" is explained by a misrepresentation of the heights of the two triangles. The presenter should be made to cut his triangles from inch-thick, six foot by ten foot steel plate so that the rounding difference would show up.

 

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Posted : April 12, 2021 8:20 am
Brad Ott liked
Bill93
(@bill93)
5,000+ posts Member
Posted by: @mathteacher

That's a different interpretation from mine, but equally valid since we can't put a micrometer to his cutouts.

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Posted : April 12, 2021 9:10 am

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