Question 1091799
Let {{{ x }}} = liters of 20% solution needed
{{{ ( .2x + .35*450 ) / ( x + 450 ) = .3 }}}
{{{ .2x + 157.5 = .3*( x + 450 ) }}}
{{{ .2x + 157.5 = .3x + 135 }}}
{{{ .1x = 22.5 }}}
{{{ x = 225 }}}
225 liters of 20% solution must be added
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check:
{{{ ( .2*225 + .35*450 ) / ( 225 + 450 ) = .3 }}}
{{{ ( 45 + 157.5 ) / 675 = .3 }}}
{{{ 202.5 = .3*675 }}}
{{{ 202.5 = 202.5 }}}
OK