Fun with the HP 30b
Introduction
The
following programs are for the HP 30b Business Professional. Did you
know that the 30b has a programming mode? The program mode has room
for 10 programs with a total of 290 steps, where each key press is
counted. Thankfully, shifts and hold-shifts are merged steps.
I
couldn’t get the MSG or R/S commands to work properly. Therefore I
use an approach that I often use for the Voyager calculators (HP 11C,
12C, 15C): store everything first and then run the program.
Disp5
is like the PSE (pause) command, it stops the execution for a second.
Disp can be set to 1-9. Disp1 lasts for 1/5 second.
All
programs are done in the Algebraic instead of the RPN I usually do on
HP calculators.
All
the results in the examples, except the last one, are rounded to four
decimal places.
Program
0: f(x,y) = (x * y) / (x + y)
f(x,
y) = (x * y) / (x + y)
Store
x in memory 1 and y in memory 2.
Prog
0 =
RCL
1
×
RCL
2
÷
(
↓
RCL
1
+
RCL
2
)
Swap
=
Stop
Examples:
x =
1.5, y = 16; Result: 1.3714
x =
3.6, y = 32; Result: 3.2360
x =
8.7, y = 10; Result: 4.6524
Program
1: PITI – Principal, Interest, Taxes, and Insurance
This
program calculates the monthly payment of PI (principal and interest)
and PITI (principal, interest, taxes, and insurance). The program
assumes that payments per year setting (P/YR) is set to 12.
Store
to Memory:
M1:
Annual insurance rate.
M2:
Annual property tax rate.
N:
number of payments
I/YR:
interest rate of the loan
PV:
amount of the loan
It
assumed that there is no balloon payment (FV = 0), although this
program can be modified to include balloon payments by removing the
first two steps (0 FV).
Prog
1 =
0
FV
PMT
Disp5
Disp5
–
(
R↓
RCL
1
+
RCL
2
)
Swap
/
1
2
0
0
*
RCL
PV
=
Stop
Examples:
N =
360
I/YR
= 8.9%
PV =
289000
Insurance
Rate = 1% (1 STO 1)
Property
Tax Rate = 1.3% (1.3 STO 2)
Result:
PMT:
-2304.60
PITI:
-2858.51
N =
360
I/YR
= 8.9%
PV =
289000
Insurance
Rate = 1% (1 STO 1)
Property
Tax Rate = 1.3% (1.3 STO 2)
Result:
PMT:
-2304.60
PITI:
-2858.51
Program
2: Quadratic Equation – Po-Shen Lo Method
This
program solves the monic quadratic polynomial:
x^2
+ B * x + C = 0
where
the solutions:
U^2
= B^2 / 4 – C
x1,
x2 = – B / 2 ± √(U^2)
Store
to Memory:
M1:
B
M2:
C
Prog
2 =
RCL
1
X^2
/
4
–
RCL
2
=
√
STO
0
–
RCL
1
/
2
=
STO
3
Disp5
Disp5
–
2
*
RCL
0
=
STO
4
Stop
M3:
root 1 ( -B / 2 + √(U^2) )
M4:
root 1 ( -B / 2 + √(U^2) )
This
program finds real roots only. If there are no real roots, then the
program displays an error.
Examples:
x^2
– 2 * x – 24 = 0
B =
-2 STO 1
C =
-24 STO 2
Roots:
6, -4
x^2
– 10 * x + 21 = 0
B =
-10 STO 1
C =
21 STO 2
Roots:
3, 7
Program
3: Lease with Advanced Payments (HP 12C – see source)
This
program calculates the regular monthly payment of a lease when the
borrower pays a set number of payments in advance. Payments per
year (P/YR) is assumed to be set at 12 while the calculator is set to
End of Period payments.
Store
in Memory:
number
of payments [ N ]
annual
lease rate [ I/YR ]
residual
value [ FV ]
number
of payments to be made in advance [ STO ] 0
loan
amount [ STO ] 1 (not PV)
Prog
3 =
0
PMT
0
PV
PV
+
RCL
1
=
STO
2
0
FV
RCL
N
–
RCL
0
=
N
1
+/-
PMT
(
R↓
PV
+
RCL
0
)
Swap
1/X
*
RCL
2
=
Stop
Examples:
Total
Payments: 48 [ N ]
Rate:
13 [ I/YR ]
Residual
Value: 7,000 [ FV ]
Payments
in Advance: 1 [ STO ] 0
Loan
Amount: 25,000 [ STO ] 1
Result:
-536.06
Total
Payments: 60 [ N ]
Rate:
8.8 [ I/YR ]
Residual
Value: 12,000 [ FV ]
Payments
in Advance: 3 [ STO ] 0
Loan
Amount: 118,000 [ STO ] 1
Result:
-2,229.71
For
those of you in the United States, Happy Thanksgiving!
Source
Hewlett
Packard. HP 12C Financial Calculator: User’s Guide.
Edition 5. 2008. San Diego, CA. pp. 124-126
Eddie
All
original content copyright, © 2011-2024. Edward Shore.
Unauthorized use and/or unauthorized distribution for commercial
purposes without express and written permission from the author is
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