Question 728071
Let {{{ a }}} = kg of copper needed
Let {{{ b }}} = kg of tin needed
(1) {{{ 8.9a + 9.5b = 9.1*16.6 }}}
(2) {{{ a + b = 16.6 }}}
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(1) {{{ 890a + 950b = 15106 }}}
Multiply both sides of (2) by {{{ 890 }}}
and subtract (2) from (1)
(1) {{{ 890a + 950b = 15106 }}}
(2) {{{ -890a - 890b = -14774 }}}
{{{ 60b = 332 }}}
{{{ b = 5.5333 }}}
and
(2) {{{ a + b = 16.6 }}}
(2) {{{ a + 5.5333 = 16.6 }}}
(2) {{{ a = 11.0667 }}}
11.0667 kg of copper is needed
5.5333 kg of tin is needed
check answer:
(1) {{{ 8.9a + 9.5b = 9.1*16.6 }}}
(1) {{{ 8.9*11.0667 + 9.5*5.5333 = 151.06 }}}
(1) {{{ 98.49363 + 52.56635 = 151.06 }}}
(1) {{{ 151.05998 = 151.06 }}}
close enough