Question 1111575
Let {{{ a }}} = mg of 72 L/mg rock needed
Let {{{ b }}} = mg of 150 L/mg rock needed
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(1) {{{ a + b = 18000 }}}
(2) {{{ 72a + 150b = 18000*120 }}}
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(2) {{{ 72a + 150b = 2160000 }}}
(2) {{{ 12a + 25b = 360000 }}}
Multiply both sides of (1) by {{{ 12 }}} and
subtract (1) from (2)
(2) {{{ 12a + 25b = 360000 }}}
(1) {{{ -12a - 12b = -216000 }}}
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{{{ 13b = 144000 }}}
{{{ b = 11076.92 }}}
and
(1) {{{ a = 18000 - b }}}
(1) {{{ a = 18000 - 11076.92 }}}
(1) {{{ a = 6923.08 }}}
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6,923.08 mg of 72 L/mg rock
11,076.92 mg of 150 L/mg rock
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check:
(2) {{{ 72a + 150b = 2160000 }}}
(2) {{{ 72*6923.08 + 150*11076.92 = 2160000 }}}
(2) {{{ 498461.76 + 1661538 = 2160000 }}}
(2) {{{ 2159999.76 = 2160000 }}}
close enough
Definitely get a 2nd opinion on this one