Question 1154192
Let {{{ x }}} = liters of 10% acid solution needed
{{{ 8 - x }}} = liters of 40% acid solution needed
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{{{ ( .1x + .4*( 8 - x ) ) / 8 = .3 }}}
{{{ .1x + .4*( 8 - x ) = 2.4 }}}
{{{ .1x + 3.2 - .4x = 2.4 }}}
{{{ .3x = .8 }}}
{{{ x = 8/3 }}}
{{{ 2.667 }}} liters of 10% solution are needed
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check:
{{{ ( .1x + .4*( 8 - x ) ) / 8 = .3 }}}
{{{ ( .1*(8/3) + .4*( 8 - 8/3 ) ) / 8 = .3 }}}
{{{  .1*(8/3) + .4*( 8 - 8/3 ) = 2.4 }}}
{{{  .1*(8/3) + .4*( 24/3 - 8/3 ) = 2.4 }}}
{{{  .1*(8/3) + .4*( 16/3 ) = 2.4 }}}
{{{ .1*8 + .4*16 = 7.2 }}}
{{{ .8 + 6.4 = 7.2 }}}
{{{ 7.2 = 7.2 }}}
OK