Question 724361
Let {{{ x }}} = liters of 20% solution needed
{{{ .2x }}} = liters of salt in 20% solution
{{{ .6*45 = 27 }}} liters of salt in 60% solution
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( total liters of salt ) / ( total liters of solution ) = 35%
{{{ ( .2x + 27 ) / ( x + 45 ) = .35 }}}
{{{ .2x + 27 = .35*( x + 45 ) }}}
{{{ .2x + 27 = .35x + 15.75 }}}
{{{ .15x = 27 - 15.75 }}}
{{{ .15x = 11.25 }}}
{{{ x = 75 }}}
75 liters of 20% solution are needed
check:
{{{ ( .2x + 27 ) / ( x + 45 ) = .35 }}}
{{{ ( .2*75 + 27 ) / ( 75 + 45 ) = .35 }}}
{{{ ( 15 + 27 ) / 120 = .35 }}}
{{{ 42 = .35*120 }}}
{{{ 42 = 42 }}}
OK