Solve Simple Interest Applications: example 6.35

Find the rate if a principal of $$8,200$ earned $$3,772$ interest in $4$ years.

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Your turn

The book's Try It right after this example: same idea, new numbers. Only the answer is given.

Find the rate if a principal of $$5,000$ earned $$1,350$ interest in $6$ years.

How did it go?

Write the formula.	$I = P r t$
Substitute the given information.	$3,772 = 8,200 r (4)$
Multiply.	$3,772 = 32,800 r$
Divide.	$\frac{3,772}{32,800} = \frac{32,800 r}{32,800}$
Simplify.	$0.115 = r$
Write as a percent.	$11.5% = r$
Check your answer. Is 11.5% a reasonable rate if $3,772 was earned in 4 years?
$I = P r t$
$3,772 \overset{?}{=} 8,200 (0.115) (4)$
$3,772 = 3,772 ✓$
Write a complete sentence that answers the question.	The rate was 11.5%.

Write the formula.	$I = P r t$
Substitute the given information.	$3,772 = 8,200 r (4)$
Multiply.	$3,772 = 32,800 r$
Divide.	$\frac{3,772}{32,800} = \frac{32,800 r}{32,800}$
Simplify.	$0.115 = r$
Write as a percent.	$11.5% = r$
Check your answer. Is 11.5% a reasonable rate if $3,772 was earned in 4 years?
$I = P r t$
$3,772 \overset{?}{=} 8,200 (0.115) (4)$
$3,772 = 3,772 ✓$
Write a complete sentence that answers the question.	The rate was 11.5%.