HP 25 User Manual

The Automatic Memory Stack 47
Example: A bacteriologist tests a certain strain whose popu-
lation typically increases by 15 % each day. lfhe 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 0.
Press Display
1.15
1
1
.
1
5
Growth factor.
Imim
1 1.15
Imim
1 1.15
Imim
11.15
Growth factor now in T.
1000
11000.
Starting population.
0
1 1150.00
Population after I st day.
0
11322.50
Population after 2nd day.
0
1 1520.88
Population after 3rd day.
0
1
174
9.01
Population after 4th day.
0
1 2011.36
Population after 5th day.
0
1 2313.06
Population after 6th day.
When you press0the 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 0
causes the number in the T-register to be duplicated each
time the stack is dropped. However , the mJ key , since it
rotates the contents of the stack registers , does not rCll'ritc any
number , but merely shifts the numbers that are already in
the stack.

HP 25 Specifications

General

Power Source	Rechargeable battery pack
Programming Steps	49
Release Year	1975
Functions	Trigonometric, logarithmic, statistical
Type	Scientific
Dimensions	148 x 80 x 14 mm