Question 1003165
Let {{{ x }}} = litres of water to be added
{{{ 22 - x }}} = litres of pure milk that you started with
{{{ .89*( 22 - x ) }}} = litres of water in the pure milk
that you started with
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I can say:
{{{ ( x + .89*( 22-x ) ) / 22 = .9 }}}
{{{ x + .89*( 22-x ) = .9*22 }}}
{{{ x + 19.58 - .89x = 19.8 }}}
{{{ .11x = .22 }}}
{{{ x = 2 }}}
2 litres of water has to be added
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check:
{{{ ( x + .89*( 22-x ) ) / 22 = .9 }}}
{{{ ( 2 + .89*( 22-2 ) ) / 22 = .9 }}}
{{{ 2 + .89*20 = .9*22 }}}
{{{ 2 + 17.8 = 19.8 }}}
{{{ 19.8 = 19.8 }}}
OK