Lesson
#3
Interest Calculations
This lesson illustrates the use
of
variables and the assignment
of
values to variables.
Applications to the calculation
of
interest and mortgage payments will serve as useful
examples
of
the use
of
variables in BASIC programs.
The programs used in this and all the following lessons will be explained line
by
line
to give you a thorough understanding
of
the operations and the concepts involved.
Experiment
#1
Simple interest
If
P dollars are borrowed at the simple interest rate
r,
then the amount S that must be
repaid after
t years is given
by
the fonnula
S =
P(l
+ rt)
S is called the sum and P is the principal. The first program in this lesson calculates S
for the following values
of
P,
rand
t:
P = $10,000
r = 18%
per
year
t
= 10 years
CarefUlly enter the following program into the Computer:
10
P
=
1111000
2
III
R
=
•
18
3
III
T
=
10
L10
5
=
P
*
( 1
+ R
*
T>
50
PRINT
"THE
SUM
IS
$"
;
5
After the program is entered, execute it by entering the
RUN
command
or
pressing the
RUN
Function Key, (fj).
The
output from the program should
be:
THE
SUM
IS
$
28000
Ok
•
If
$10,000 is borrowed for 10 years at the simple interest
of
18%, you will have to
pay back
$28,000.
31
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