Question 1111897
Use simple interest formula
{{{ I = P*r*t }}}
Let {{{ I }}} = interest earned from 8% investment
{{{ 1640 - I }}} = interest earned from 11% investment
Let {{{ P }}} = amount invested at 8%
{{{ 3P }}} = amount invested at 11%
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For 8% investment:
(1) {{{ I = P*.08*1 }}}
For 11% investment:
(2) {{{ 1640 - I = 3P*.11*1 }}}
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(1) {{{ I = .08P }}}
and
(2) {{{ 1640 - I = .33P }}}
Plug (1) into (2)
(2) {{{ 1640 - .08P = .33P }}}
(2) {{{ .41P = 1640 }}}
(2) {{{ P = 4000 }}}
and
{{{ 3P = 12000 }}}
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$4,000 was invested @ 8%
$12,000 was invested @ 11%