Question 750537
You can assume that this is a juice and water mixture.
Let {{{ x }}} = the cups of pure juice to be added
{{{ .05*40 = 2 }}} cups of pure juice in 5% mixture
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{{{ ( 2 + x ) / ( 40 + x ) = .1 }}}
{{{ 2 + x = .1*( 40 + x ) }}}
{{{ 2 + x = 4 + .1x }}}
{{{ .9x = 2 }}}
{{{ x = 2.222 }}}
2.222 cups of pure juice are needed
check:
{{{ ( 2 + x ) / ( 40 + x ) = .1 }}}
{{{ ( 2 + 2.222 ) / ( 40 + 2.222 ) = .1 }}}
{{{ 4.222 / 42.222 = .1 }}}
{{{ .1 = .1 }}}
OK