Question 1087124
Let {{{ x }}} = liters of 10% acid solution needed
{{{  12 - x }}} = liters of pure acid needed
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{{{ ( .1x + ( 12 - x )) / 12 = .3 }}}
{{{ .1x + 12 - x = 3.6 }}}
{{{ .9x = 12 - 3.6 }}}
{{{ .9x = 8.4 }}}
{{{ x = 9.33 }}}
9.33 liters of 10% acid solution is needed
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check answer:
{{{ ( .1x + ( 12 - x )) / 12 = .3 }}}
{{{ ( .1*9.333 + ( 12 - 9.333 )) / 12 = .3 }}}
{{{ ( .9333 + 2.667 ) / 12 = .3 }}}
{{{ 3.6 = .3*12 }}}
{{{ 3.6 = 3.6 }}}
OK