Question

bridget deposited $9,000 in a savings account with simple interest. four months later, she had earned $30 in interest. what was the interest rate? use the formula $i = prt$, where $i$ is the interest earned, $p$ is the principal (starting amount), $r$ is the interest rate expressed as a decimal, and $t$ is the time in years.

Explanation:

Step1: Identify given values

We know \( i = 30 \), \( p = 9000 \), and \( t \) (time in years). Since the time is 4 months, we convert it to years: \( t=\frac{4}{12}=\frac{1}{3} \) years.

Step2: Substitute into the formula \( i = prt \)

Substitute the known values into the formula: \( 30 = 9000\times r\times\frac{1}{3} \).

Step3: Solve for \( r \)

First, simplify the right - hand side: \( 9000\times\frac{1}{3}=3000 \), so the equation becomes \( 30 = 3000r \). Then, divide both sides by 3000: \( r=\frac{30}{3000}=0.01 \).

Step4: Convert \( r \) to a percentage

To convert the decimal \( r = 0.01 \) to a percentage, we multiply by 100: \( 0.01\times100 = 1\% \).

Answer:

\( 1 \)