Question 1049113
Let {{{ x }}} = ml of the 75% solution needed
{{{ .3*65 = 19.5 }}} = ml of concentrate in the 30% solution
{{{ .75x }}} = ml of concentrate in the 75% solution
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{{{ ( 19.5 + .75x ) / ( 65 + x ) = .35 }}}
{{{ 19.5 + .75x = .35*( 65 + x ) }}}
{{{ 19.5 + .75x = 22.75 + .35x }}}
{{{ .4x = 22.75 - 19.5 }}}
{{{ .4x = 3.25 }}}
{{{ x = 8.125 }}}
8.125 ml of the 75% solution is needed
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check answer:
{{{ ( 19.5 + .75x ) / ( 65 + x ) = .35 }}}
{{{ ( 19.5 + .75*8.125 ) / ( 65 + 8.125 ) = .35 }}}
{{{ ( 19.5 + 6.09375 ) / 73.125 = .35 }}}
{{{ 25.59375 / 73.125 = .35 }}}
{{{ 25.59375 = .35*73.125 }}}
{{{ 25.59375 = 25.59375 }}}
OK