o 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
example 26 by use of the CI scale, proceed exactly as if you were going
to multiply in the usual manner except that you use the CI scale instead
of the C scale. First set the left-hand index of the C scale over 14 on
the D scale. Then move the indicator to 2 on the CI scale. Read the
result, 7, on the D scale under the hair-line. This is really another
way of dividing. THE READER IS ADVISED TO WORK EXAMPLES 16 TO 25 OVER
AGAIN BY USE OF THE CI SCALE.

SQUARING AND SQUARE ROOT

If we take a number and multiply it by itself we call the result the
square of the number. The process is called squaring the number. If we
find the number which, when multiplied by itself is equal to a given
number, the former number is called the square root of the given number.
The process is called extracting the square root of the number. Both
these processes may be carried out on the A and D scales of a slide
rule. For example:

Example 27: 4 * 4 = square( 4 ) = 16

Set indicator over 4 on D scale. Read 16 on A scale under hair-line.

Example 28: square( 25.4 ) = 646.0

The decimal point must be placed by mental survey. We know that
square( 25.4 ) must be a little larger than square( 25 ) = 625
so that it must be 646.0.

To extract a square root, we set the indicator over the number on the A
scale and read the result under the hair-line on the D scale. When we
examine the A scale we see that there are two places where any given
number ma