Question 1046721
Let {{{ x }}} = gallons of pure acid needed
{{{ .6*2 = 1.2 }}} = gallons of pure acid in 60% solution
---------------------
{{{ ( x + 1.2 ) / ( x + 2 ) = .9 }}}
{{{ x + 1.2 = .9*( x + 2 ) }}}
{{{ x + 1.2 = .9x + 1.8 }}}
{{{ .1x = .6 }}}
{{{ x = 6 }}}
-------------
6 gallons of pure acid are needed
-------------
check:
{{{ ( x + 1.2 ) / ( x + 2 ) = .9 }}}
{{{ ( 6 + 1.2 ) / ( 6 + 2 ) = .9 }}}
{{{ 7.2 / 8 = .9 }}}
{{{ 7.2 = .9*8 }}}
{{{ 7.2 = 7.2 }}}
OK