Question

119. Beatrice decides to deposit $100 per month at the end of every month in a bank with an annual interest rate of 5.5% compounded monthly.
a. Write a geometric series to show how much she will accumulate in her account after one year.

Answer 1

Answer:

Beatrice will accumulate $1230.72 at the end of the year.

Step-by-step explanation:

We can write:

$(1+\frac{0.055}{12})=z$

$100=C$ for deposits

The first month would have only the deposit reflected in her balance, then, expanding some steps of the calculation would yield:

$S_{1}=C\\S_{2}=Cz + C\\S_{3}=Cz^{2}+Cz + C\\S_{n}=Cz^{n-1} +...+Cz+C$

A geometric series is given by:

$1+x+...+x^{m}=\frac{x^{m+1}-1}{x-1}$

Translating our series to the short form:

$S_{n}=C(\frac{z^{n}-1}{z-1} )$

plugin in the values for the 12 month gives:

$S_{12}=100(\frac{(1+\frac{0.055}{12})^{12} -1}{\frac{0.055}{12}})=1230.7169$