Question 1111156
There is a border on both sides of the 12 in
side, so that each side is {{{ 12 + 2x }}} in long
Also, there is a border on each side of the
16 in side, so this side is {{{ 16 + 2x }}} in long
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Add up the inside area and the ares of the border.
{{{ 12*16 + 128 = 192 + 128 }}}
{{{ 192 + 128 = 320 }}} in2
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Now I can say:
{{{ ( 12 + 2x )*( 16 + 2x ) = 320 }}}
{{{ 192 + 32x + 24x + 4x^2 = 320 }}}
{{{ 4x^2 + 56x - 128 = 0 }}}
{{{ x^2 + 14x - 32 = 0 }}}
{{{ ( x + 16 )*( x - 2 ) = 0 }}} ( by observation )
{{{ x = 2 }}} ( can only use the positve result )
The width of the border is 2 in
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check:
{{{ ( 12 + 2*2 )*( 16 + 2*2 ) = 320 }}}
{{{ 16*20 = 320 }}}
{{{ 320 = 320 }}}
OK