Question 610689
Let {{{ x }}} = ml of water to be added
{{{ .75*50 = 37.5 }}} ml of acid in 75% solution
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{{{ 37.5 / ( 50 + x ) = .15 }}}
{{{ 37.5 = .15*( 50 + x ) }}}
{{{ 37.5 = 7.5 + .15x }}}
{{{ .15x = 37.5 - 7.5 }}}
{{{ .15x = 30 }}}
{{{ x = 200 }}}
200 ml of water must be added
check:
{{{ 37.5 / ( 50 + 200 ) = .15 }}}
{{{ 37.5 = .15*250 }}}
{{{ 37.5 = 37.5 }}}
OK