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Riley invested her work bonus in a bond with a monthly simple interest rate of 0.8%. The bond earned her $5,016 total,of which $2,016 was interest. How many years was the money invested?

Answer :

the total amount she have at the end was $5,016 dollars of which $2,016 was interenst, so with this information we know that at the beginig the save:

[tex]5016-2016=3000[/tex]

now we can write the formula like:

[tex]5016=3000(1+0.08)^t[/tex]

where t is the number of years, so we can solve for t

[tex]\begin{gathered} \frac{5016}{3000}=(1+0.08)^t \\ 1.672=(1+0.08)^t \end{gathered}[/tex]

now we use the log properties so:

[tex]\begin{gathered} \ln (1.678)=t\ln (1+0.08) \\ t=\frac{\ln (1.672)}{\ln (1.08)} \\ t=6.68 \end{gathered}[/tex]