HP HP-25 User Manual

Example: A bacteriologist tests a certain strain whose popu-
lation typically increases by 15% each day. If he starts a sample
culture of 1000, what will be the bacteria population at the end
of each day for six consecutive days?
Method: Put the growth factor (1.15) in the Y-, Z-, and T-
registers and put the original population (1000) in the X-register.
Thereafter, you get the new population whenever you press[x].
Press Display
1.15 1.15 Growth factor.
EnEl [1.15
1.15
1.15 Growth factor now in T.
1000 1000. Starting population.
1150.00 Population after Ist day.
1322.50 Population after 2nd day.
1520.88 Population after 3rd day.
1749.01 Population after 4th day.
2011.36 Population after Sth day.
2313.06 Population after 6th day.
()
X
[x]
X
[x]
[X]
When you press[x]the first time, you calculate 1.15 x 1000. The
result (1150.00) is displayed in the X-register and a new copy of
the growth factor drops into the Y-register. Since a new copy of
the growth factor is duplicated from the T-register each time the
stack drops, you never have to reenter it.
Notice that performing a two-number operation such as [x]
causes the number in the T-register to be duplicated each
time the stack is dropped. However, the [ key, since it
rotates the contents of the stack registers, does not rewrite any
number, but merely shifts the numbers that are already in
the stack.

HP HP-25 Specifications

General

Brand	HP
Model	HP-25
Category	Calculator
Language	English