Question 617197
Let {{{ a }}} = ounces of 10% solution used
Let {{{ b }}} = ounces of 20% solution used
{{{ .1a }}} =  ounces of glucose in 10% solution
{{{ .2b }}} =  ounces of glucose in 20% solution
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given:
(1) {{{ a + b = 16 }}}
(2) {{{ ( .1a + .2b ) / 16 = .18 }}}
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(2) {{{ .1a + .2b = .18*16 }}}
(2) {{{ .1a + .2b = 2.88 }}}
(2) {{{ 10a + 20b = 288 }}}
(2) {{{ 5a + 10b = 144 }}}
Multiply both sides of (1) by {{{5}}}
and subtract from (2)
(2) {{{ 5a + 10b = 144 }}}
(1) {{{ -5a - 5b = -80 }}}
{{{ 5b = 64 }}}
{{{ b = 12.8 }}}
and
(1) {{{ a + b = 16 }}}
(1) {{{ a + 12.8 = 16 }}}
(1) {{{ a = 3.2 }}}
3.2 ounces of 10% solution is used
12.8 ounces of 20% solution is used
check:
(2) {{{ ( .1*3.2 + .2*12.8 ) / 16 = .18 }}}
(2) {{{ .32 + 2.56 = .18*16 }}}
(2) {{{ 2.88 = 2.88 }}}
OK