Question 746115
Let {{{ a }}} = pints of 1% solution needed
Let {{{ b }}} = pints of 4% solution needed
{{{ .01a }}} = peroxide in 1% solution
{{{ .04b }}} = peroxide in 4% solution
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(1) {{{ a + b = 10 }}}
(2) {{{ ( .01a + .04b ) / 10 = .02 }}}
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(2) {{{ .01a + .04b = .2 }}}
(2) {{{ a + 4b = 20 }}}
Subtract (1) from (2)
(2) {{{ a + 4b = 20 }}}
(1) {{{ -a - b = -10 }}}
{{{ 3b = 10 }}}
{{{ b = 3.333 }}}
and, since
(1) {{{ a + b = 10 }}}
(1) {{{ a + 3.333 = 10 }}}
(1) {{{ a = 6.667 }}}
6.667 pints of 1% solution are needed
3.333 pints of 4% solution are needed
check:
(2) {{{ ( .01*6.667 + .04*3.333 ) / 10 = .02 }}}
(2) {{{ ( .0667 + .1333 ) / 10 = .02 }}}
(2) {{{ .2 = 10*.02 }}}
(2) {{{ .2 = .2 }}}
OK