Section ii • USing the Simple intereSt FormUla 313
Using the simple interest FormUla
In Section I, we used the simple interest formula,
, to solve for the interest. Frequently
in business, however, the principal, rate, or time might be the unknown factor. Remember
from Chapter 5 that an equation can be solved for any of the variables by isolating that vari-
able to one side of the equation. In this section, we convert the simple interest formula to
equations that solve for each of the other variable factors.
solving For the principal
10-6
When using the simple interest formula to solve for principal,
, we isolate the
on one side of
the equation by dividing both sides of the equation by
. This yields the new equation as follows:
Business Decision: competing Banks
48. You are the accounting manager for Kool Ragz, Inc., a manufacturer of men’s and women’s
clothing. The company needs to borrow
for
days in order to purchase a large
quantity of material at “closeout” prices. The interest rate for such loans at your bank, Rimrock
Bank, is
using ordinary interest.
a. What is the amount of interest on this loan?
b. After making a few “shopping” calls, you find that Southside National Bank will lend at
using exact interest. What is the amount of interest on this offer?
c. So that you can keep your business, Rimrock Bank has offered a loan at
using
ordinary interest. What is the amount of interest on this offer?
d. (Challenge) If Southside National wants to beat Rimrock’s last offer (part c) by charging
less interest, what rate, rounded to the nearest hundredths of a percent, must it quote
using exact interest?
There are approximately
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Section ii
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