Question 744895
Let {{{ w }}} = pints of water needed
{{{ .5*2 = 1 }}} pint of developer in 50% solution
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{{{ 1 / ( 2 + w ) = .31 }}}
{{{ .31*( 2 + w ) = 1 }}}
{{{ 2 + w = 1/.31 }}}
{{{ w = 3.2258 - 2 }}}
{{{ w = 1.2258 }}} pints
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check:
{{{ 1 / ( 2 + w ) = .31 }}}
{{{ 1 / ( 2 + 1.2258 ) = .31 }}}
{{{ 1 / 3.2258 = .31 }}}
{{{ .31 = .31 }}}
OK