Question 911762
Marsha and Kan both invested money on March 1, 2007.
 Marsha invested $9,000 at Bank A where the interest was compounded quarterly.
 Jan invested $6,000 at Bank B where the interest was compounded continuously.
 On March 1, 2012, Marsha had a balance of $11,789.68 while Jan had a balance of $7,504.50.
 What was the interest at each bank?
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From the information given, we know both had money invested for 5 yrs
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M
{{{9000(1+(r/4))^(5*4)}}} = 11789.68
{{{(1+(r/4))^20}}} = {{{11789.68/9000}}}
use logs here
{{{log((1+(r/4))^20)}}} = {{{log(11789.68/9000)}}}
{{{log((1+(r/4))^20)}}} = .1172595
{{{log((1+(r/4)))}}} = {{{1172595/20}}}
{{{log(1+(r/4))}}} = .005862975
find the antilog
1 + {{{r/4}}} = 1.0136
{{{r/4}}} = 1.0136 - 1
{{{r/4}}} = .0136 
mult both sides fy 4
r = .054366 ~ 5.44% interest
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J
{{{6000*e^(5r)}}} = 7504.50
{{{e^(5r)}}} = {{{7504.50/6000}}}
use natural logs here, ln of e = 1, so we have a simple equation
5r =  {{{ln(7504.50/6000)}}}
5r = .21046
r = {{{.2237/5}}}
r = .04475 ~ 4.475% interest
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