Question 944272
Let {{{ a }}} = ml of 14% solution needed
Let {{{ b }}} = ml of 38% solution needed
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(1) {{{ a + b = 120 }}}
(2) {{{ ( .14a + .38b ) / 120 = .3 }}}
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(2) {{{ .14a + .38b = .3*120 }}}
(2) {{{ .14a + .38b = 36 }}}
(2) {{{ 14a + 38b = 3600 }}}
Multiply both sides of (1) by {{{ 14 }}}
and subtract (1) from (2)
(2) {{{ 14a + 38b = 3600 }}}
(1) {{{ -14a - 14b = -1680 }}}
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{{{ 24b = 1920 }}}
{{{ b = 80 }}}
and, since
(1) {{{ a + b = 120 }}}
(1) {{{ a = 40 }}}
40 ml of 14% solution is needed
80 ml of 38% solution is needed
check:
(2) {{{ ( .14*40 + .38*80 ) / 120 = .3 }}}
(2) {{{ ( 5.6 + 30.4 ) / 120 = .3 }}}
(2) {{{ 36 = .3*120 }}}
(2) {{{ 36 = 36 }}}
OK