We are given the formula for the simple interest

I

earned on an account where an amount

p

is deposited at an interest rate

r

for a certain number of years

t .

I = p r t

Let's consider the given table that shows the details of the three different accounts.

Accounts at First Savings Bank
Account	$p$ $($)$	$r$ $(%)$
A	$350$	$4$
B	$500$	$3.5$
C	$280$	$4.25$

We want to order the accounts from least to greatest interest earned after

5

years. To do so, we will first find the value of each interest earned after

5

years. Let's start by finding the interest earned on Account A. We will substitute

350

for

p,

4 %

for

r,

and

5

for

t

into the formula.

I = p r t \Leftrightarrow I = 350 \cdot 4 % \cdot 5

To calculate the product, we will rewrite

4 %

as a decimal number. We can rewrite a percent as a decimal by ignoring the percent symbol and moving the decimal point two places to the left.

Now we can find the value of

I

for the first account.

I = 350 \cdot 4 % \cdot 5

WriteDec

Write as a decimal

I = 350 \cdot 0.04 \cdot 5

Multiply

I = 14 \cdot 5

Multiply

I = 70

Next, let's find the interest on Account B. Let's substitute

500

for

p,

3.5 %

for

r,

and

5

for

t

into the formula.

I = p r t \Leftrightarrow I = 500 \cdot 3.5 % \cdot 5

Let's rewrite

3.5 %

as a decimal.

Now we can find the value of

I

for Account B.

I = 500 \cdot 3.5 % \cdot 5

WriteDec

Write as a decimal

I = 500 \cdot 0.035 \cdot 5

Multiply

I = 17.5 \cdot 5

Multiply

87.5

Next, we will find the interest on Account C. Let's substitute

280

for

p,

4.25 %

for

r,

and

5

for

t

into the formula.

I = p r t \Leftrightarrow I = 280 \cdot 4.25 % \cdot 5

Let's rewrite

4.25 %

as a decimal. One again, we ignore the percent symbol and move the decimal point two places to the left.

Let's find the value of

I

for the account C.

I = 280 \cdot 4.25 % \cdot 5

WriteDec

Write as a decimal

I = 180 \cdot 0.0425 \cdot 5

Multiply

I = 11.9 \cdot 5

Multiply

I = 59.5

We found the interests on each account. Let's make a new column in the table with the value of interest after

5

years.

Accounts at First Savings Bank
Account	$p$ $($)$	$r$ $(%)$	Interest $I$ after $5$ years
A	$350$	$4$	$70$
B	$500$	$3.5$	$87.5$
C	$280$	$4.25$	$59.5$

The account with the least amount of interest earned is Account C, and account with the greatest is Account B. Therefore, we can finally order the accounts from least to greatest interest earned.

C, A, B

Exercise