Question 860275
Let {{{ a }}} = amount invested @ 12%
Let {{{ b }}} = amount invested @ 5.25%
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(1) {{{ a + b = 21000 }}}
(2) {{{ .12a + .0525b = 2250 }}}
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(2) {{{ 1200a + 525b = 22500000 }}}
(2) {{{ 16a + 7b = 300000 }}}
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Multiply both sides of (1) by {{{ 7 }}}
and subtract (1) from (2)
(2) {{{ 16a + 7b = 300000 }}}
(1) {{{ -7a - 7b = -147000 }}}
{{{ 9a = 153000 }}}
{{{ a = 17000 }}}
and
(1) {{{ 17000 + b = 21000 }}}
(1) {{{ b = 4000 }}}
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$17,000 is invested @ 12% and
$4,000 is invested @ 5.25%
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check:
(2) {{{ .12a + .0525b = 2250 }}}
(2) {{{ .12*17000 + .0525*4000 = 2250 }}}
(2) {{{ 2040 + 210 = 2250 }}}
(2) {{{ 2250 = 2250 }}}
OK