Question 1091495
Let {{{ a }}} = amount to invest @ 10%
Let {{{ b }}} = amount to invest @ 15%
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(1) {{{ a + b = 90000 }}}
(2) {{{ .1a + .15b = 10000 }}}
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(2) {{{ 10a + 15b = 1000000 }}}
(2) {{{ 2a + 3b = 200000 }}}
Multiply both sides of (1) by {{{ 2 }}}
and subtract (1) from (2)
(2) {{{ 2a + 3b = 200000 }}}
(1) {{{ -2a -2b = -180000 }}}
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{{{ b = 20000 }}}
and
(1) {{{ a + b = 90000 }}}
(1) {{{ a + 20000 = 90000 }}}
(1) {{{ a = 70000 }}}
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She should invest R70 000 @ 10% and
R20 000 @ 15%
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check:
(2) {{{ .1a + .15b = 10000 }}}
(2) {{{ .1*70000 + .15*20000 = 10000 }}}
(2) {{{ 7000 + 3000 = 10000 }}}
OK