Question 944815
{{{ .4*10 = 4 }}} liters of acid in 10L bottle
Let {{{ x }}} = liters of 20% solution needed
{{{ .2x }}} = liters of acid in 20% solution
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{{{ ( 4 + .2x ) / ( 10 + x ) = .35 }}}
{{{ 4 + .2x = .35*( 10 + x ) }}}
{{{ 4 + .2x = 3.5 + .35x }}}
{{{ .15x = .5 }}}
{{{ x = 3.333 }}}
3 and 1/3 liters of the 20% solution are needed
check:
{{{ ( 4 + .2x ) / ( 10 + x ) = .35 }}}
{{{ ( 4 + .2*3.333 ) / ( 10 + 3.333 ) = .35 }}}
{{{ 4.667 / 13.333 = .35 }}}
{{{ 4.667 = 4.667 }}}
OK