Question 704199
Let {{{ w }}} = ounces of water needed
Let {{{ x }}} = ounces of 20% glucose solution needed
{{{ .2x }}} = ounces of glucose in 20% solution
given:
(1) {{{ w + x = 7 }}}
(2) {{{ .2x / ( x + w ) = .1 }}}
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(2) {{{ .2x = .1*( x + w ) }}}
(2) {{{ .2x = .1x + .1w }}}
(2) {{{ .1x = .1w }}}
(2) {{{ x = w }}}
So, I can say
(1) {{{ w + x = 7 }}}
(1) {{{ 2x = 7 }}}
(1) {{{ x = 3.5 }}}
{{{ w = 3.5 }}}
3.5 ounces of water should be used
check:
(2) {{{ .2x / ( x + w ) = .1 }}}
(2) {{{ .2*3.5 / ( 3.5 + 3.5 ) = .1 }}}
(2) {{{ .7 / 7 = .1 }}}
(2) {{{ .7 = .7 }}}
OK