A bank offers 5.00% on savings accounts. What is the effective annual rate if interest is compounded semi-annually?

2 answers

To find the effective annual rate (EAR) when interest is compounded semi-annually, you can use the following formula:

\[ \text{EAR} = \left(1 + \frac{r}{n}\right)^{n \cdot t} - 1 \]

Where:

  • \( r \) is the nominal interest rate (as a decimal),
  • \( n \) is the number of compounding periods per year,
  • \( t \) is the number of years.

In this case:

  • The nominal interest rate \( r = 0.0500 \) (5.00%),
  • The number of compounding periods per year \( n = 2 \) (since the interest is compounded semi-annually),
  • We will calculate for \( t = 1 \) year.

Plugging in the values:

\[ \text{EAR} = \left(1 + \frac{0.0500}{2}\right)^{2 \cdot 1} - 1 \]

Now we calculate \( \frac{0.0500}{2} \):

\[ \frac{0.0500}{2} = 0.0250 \]

Now we compute:

\[ \text{EAR} = \left(1 + 0.0250\right)^{2} - 1 = \left(1.0250\right)^{2} - 1 \]

Next, we calculate \( (1.0250)^{2} \):

\[ (1.0250)^{2} = 1.050625 \]

So,

\[ \text{EAR} = 1.050625 - 1 = 0.050625 \]

Finally, converting back to percentage:

\[ \text{EAR} = 0.050625 \times 100 = 5.0625% \]

Thus, the effective annual rate when interest is compounded semi-annually at a nominal rate of 5.00% is 5.0625%.

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