14:  3.14 * 25 = 78.5



DIVISION

Since multiplication and division are inverse processes, division on a
slide rule is done by making the same settings as for multiplication,
but in reverse order. Suppose we have the example:

Example 15: (6.70 / 2.12) = 3.16


Set indicator over the dividend 6.70 on the D scale. Move the slider
until the divisor 2.12 on the C scale is under the hair-line. Then read
the result on the D scale under the left-hand index of the C scale. As
in multiplication, the decimal point must be placed by a separate
process. Make all the digits except the first in both dividend and
divisor equal zero and mentally divide the resulting numbers. Place the
decimal point in the slide rule result so that it is nearest to the
mental result. In example 15, we mentally divide 6 by 2. Then we place
the decimal point in the slide rule result 316 so that it is 3.16 which
is nearest to 3.

A group of examples for practice in division follow:

Example
16:   34 / 2 = 17


17:   49 / 7 = 7


18:  132 / 12 = 11


19:  480 / 16 = 30


20: 1.05 / 35 = .03


21: 4.32 / 12 = .36


22: 5.23 / 6.15 = .85


23: 17.1 / 4.5 = 3.8


24: 1895 / 6.06 = 313


25:   45 /.017 = 2647



THE CI SCALE

If we divide one (1) by any number the answer is called the reciprocal
of the number. Thus, one-half is the reciprocal of two, one-quarter is
the reciprocal of four. If we take any number, say 14, and multiply it
by the reciprocal of another number, say 2, we get:

Example 26: 14 * (1/2) = 7


which is the same as 14 divided by two. This process can be carried out
directly on the slide rule by use of the CI scale. Numbers on the CI
scale are reciprocals of those on the C scale. Thus we see that 2 on the
CI scale comes directly over 0.5 or 1/2 on the C scale. Similarly 4 on
the CI scale comes over 0.25 or 1/4 on the C scale, and so on. To do