Question 1036922
I get the same area for the hexagonal prism
{{{ A = 6s*( a + h ) }}}
{{{ s = 6 }}}
{{{ a = 3*sqrt(3) }}}
{{{ h = 27 }}}
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{{{ A = 6*6*( 3*sqrt(3) + 27 ) }}}
{{{ A = 108*sqrt(3) + 972 }}}
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By removing 2 adjacent triangular prisms,
The first obvious thing is you remove 2 of 
the rectangular faces, so you have:
{{{ A[2] = 6s*( a + h ) - 2*s*h }}}
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You have created 2 new areas internal to the hexagonal
prism. Each one has an area of {{{ s*h }}}
So, now you have:
{{{ A[3] = 6s*( a + h ) - 2*s*h + 2*s*h }}}
Now you are back to
{{{ A[3] = 6s*( a + h ) }}}
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You have also lost {{{ 1/6 + 1/6 = 1/3 }}} of both
top and bottom surfaces, 
surfaces.
Now you have:
{{{ A[4] = 6s*( a + h ) - (1/3)*( 6s*a ) }}}
{{{ A[4] = (2/3)*( 6s*a ) + 6s*h }}}
{{{ A[4] = 4s*a + 6*s*h }}}
{{{ A[4] = 4*6*3*sqrt(3) + 6*6*27 }}}
{{{ A[4] = 72*sqrt(3) + 972 }}} answer
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Check my math and ( if you can ) get a 2nd
opinion. This is a visualization problem,
which I can mess up easily