<PRE><B>Question 1005197</B>
{{{ .5*4 = 2 }}} liters of water to start with
Let {{{ x }}} liters = amount to be evaporated
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You end up with the same liters of salt you started with ( 2 liters )
{{{ 2 / ( 4 - x ) = .75 }}}
{{{ 2 = .75*( 4 - x ) }}}
{{{ 2 = 3 - .75x }}}
{{{ .75x = 1 }}}
{{{ x = 1.333 }}}
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1 and 1/3 liters must be evaporated
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check:
{{{ 2 / ( 4 - x ) = .75 }}}
{{{ 2 / ( 4 - 4/3  ) = .75 }}}
{{{ 2 / ( 8/3 ) = 3/4 }}}
{{{ 6/8 = 3/4 }}}
{{{ 3/4 = 3/4 }}}
OK</PRE>