Question 995979
Let {{{ x }}} = gallons of pure acid to be added
{{{ .4*55 = 22 }}} gallons of pure acid in 40% solution
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{{{ ( x + 22 ) / ( x + 55 ) = .5 }}}
{{{ x + 22 = .5*( x + 55 ) }}}
{{{ x + 22 = .5x + 27.5 }}}
{{{ .5x = 5.5 }}}
{{{ x = 11 }}}
11 gallons of pure acid needs to be added
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check:
{{{ ( x + 22 ) / ( x + 55 ) = .5 }}}
{{{ ( 11 + 22 ) / ( 11 + 55 ) = .5 }}}
{{{ 33/66 = .5 }}}
{{{ .5 = .5 }}}
OK