Arithmetic Calculations With Constants - HP 12C Platinum User Manual

240 Appendix A: RPN and the Stack

Arithmetic Calculations with Constants

Because the number in the T-register remains there when the stack drops, this
number can be used as a constant in arithmetic operations. To place the constant
into the T-register, key it into the display (that is, into the X-register), then press
\ three times. This also places the constant in the Y and Z-registers. Each time
an arithmetic operation is then performed — using the constant in the Y-register
and a number keyed into the displayed X-register — the constant will be
"dropped" back into the Y-register.
Example: The annual sales of solar engineering hardware your firm — currently
$84,000 — are projected to double each year for the next 3 years. Calculate the
annual sales for each of those years.
Keystrokes
(RPN mode)
2\\
\
84000
§
§
§
In the example above, the constant was repeatedly multiplied by the result of the
previous operation, which was already in the displayed X-register. In another class
of calculations with constants, the constant is multiplied by (or added to, etc.) a
new number keyed into the displayed X-register. For these calculations, you must
press O before keying in a new number after having pressed an operator key. If
this were not done, the stack would lift when you keyed in a new number after
pressing the operator key, and the Y-register would no longer contain the constant.
(Recall — from page 234 — that the stack does not lift when a number is keyed
into the displayed X-register after O is pressed.)
Display
Enters constant into Y, Z, and
2.00
T-registers.
Enters base amount into displayed
84,000.
X-register.
Annual sales after first year.
168,000.00
Annual sales after second year.
336,000.00
Annual sales after third year.
672,000.00