Question 851404
Let {{{ w }}} = liters of water to be evaporated
{{{ .2*1300 = 260 }}} liters of salt in 20% solution
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The {{{ 260 }}} liters of salt is also in the final solution
{{{ 260 / ( 1300 - w ) = .65 }}}
{{{ 260 = .65*( 1300 - w ) }}}
{{{ 260 = 845 - .65w }}}
{{{ .65w = 845 - 260 }}}
{{{ .65w = 585 }}}
{{{ w = 900 }}}
900 liters of water need to be evaporated
check:
{{{ 260 / ( 1300 - w ) = .65 }}}
{{{ 260 / ( 1300 - 900 ) = .65 }}}
{{{ 260 / 400 = .65 }}}
{{{ .65 = .65 }}}
OK