1. This rule is designed specifically for finance and business
calculations. Whilst most of the scales on this rule are standard scales, but with
different naming, it does have a few scales that are not standard.
2. The C and CF scales are the same as the C and CF on "standard" rules. The R
and RF are the equivalent to the D and DF scales on "standard" rules.
These scales lend themselves to problems of multiplication, division and proportions.
3. In this case C stands for Cost and R for Retail.
4. Two scales which are different are the C% (cost mark-up percent) and R% (retail mark-up
percent). These special scales, C% and R%, are unusual in that they run from 0 to 9, they
are in effect the values of the C and CI scales minus 1. The picture shown as "use
for mark-up" is an example of the C, R and C% scales. With the retail price of 15 (R
scale) and the cost price of 12 (C scale) the cost mark-up is 25% (C% scale) . The
picture shown as "use for discount" is an example of the C, R, and R% scales.
With a retail price of 75 (R scale) and a cost price of 60 (C scale) the discount is 20%
5. On the back of the rule are three log-log scales for compound interest problems. To
cover as wide a range of scales as possible these log-log scales are to the base 10,
rather than the more common e (2.718). The lowest value of 1.00232 this is
equivalent to a daily rate when the annual rate of interest is 2.3% and enables interest
on a daily basis.
||RF=DF [ CF, C%, C] R=D, C%
S1=LL00, S2=L01 [ C2=B, L, 1/C=CI,
C ] D, S3=LL03
Equivalent standard scale lettering shown in italics.