HP·38E/38C - Slide Rule Museum

Using Your Calculator 21
calculate the margin based on the selling price of an item, enter that
price, then key in the purchase cost and press CDI 6% I. Actually, all
percent differences follow the same rule: To find percent increase or
percent decrease, enter the old amount (base) , then key in the new
amount and press CDI 6% I. The first number (base) is retained in the
automatic memory stack.
Percent of Total I '/.T I
To find what percentage one number is of a sum of numbers, first
calculate the sum and then key in the particular number you wish to
convert to a percentage and press CD I '/. T I
1. Key in the first number.
2. Press IENTER_ I .
3. Key in subsequent numbers (if any), each followed by C±J.
4. Key in the particular number you wish to convert to a percentage
of that total.
5. Press CDI 'loT I.
Example: What percent is $5.50 of the sum of $10.25 + $5.50 +
$3.25 + $21.00? And what percent is $21.00 of the same total?
Keystrokes
10.25 IENTER_I
5.50 C±J 3.25 C±J
21 C±J
5.50 CDI '/.T I
Display
10.25
40.00
13.75
Enter the first number.
Key in and add the rest of the
numbers.
% of total.
The total is retained in the automatic memory stack-simply clear the
display, key in a new number and find I '/. T I.
Keystrokes
ICLXI
21 CDI '/.T I
Display
0.00
52.50 % of total.