e given number. Thus, since 5 * 5 * 5 = 125, 125 is the
cube of 5 and 5 is the cube root of 125.

To find the cube of any number on the slide rule set the indicator over
the number on the D scale and read the answer on the K scale under the
hair-line. To find the cube root of any number set the indicator over
the number on the K scale and read the answer on the D scale under the
hair-line. Just as on the A scale, where there were two places where you
could set a given number, on the K scale there are three places where a
number may be set. To tell which of the three to use, we must make use
of the following rule.

(a) If the number is greater than one. For 1, 4, 7, 10, etc., digits to
the left of the decimal point, use the left-hand third of the K scale.
For 2, 5, 8, 11, etc., digits to the left of the decimal point, use the
middle third of the K scale. For 3, 6, 9, 12, etc., digits to the left
of the decimal point use the right-hand third of the K scale.

(b) If the number is less than one. We now tell which scale to use by
counting the number of zeros to the right of the decimal point before
the first digit not zero. If there are 2, 5, 8, 11, etc., zeros, use the
left-hand third of the K scale. If there are 1, 4, 7, 10, etc., zeros,
then use the middle third of the K scale. If there are no zeros or 3, 6,
9, 12, etc., zeros, then use the right-hand third of the K scale. For
example:

Example 41: cube_root( 185 ) = 5.70

Since there are 3 digits in the given number, we set the indicator on
185 in the right-hand third of the K scale, and read the result 570 on
the D scale. We can place the decimal point by thinking of the nearest
perfect cube, which is 125. Therefore, the decimal point must be placed
so as to give 5.70, which is nearest to 5, the cube root of 125.

Example 42: cube_root( .034 ) = .324

Since there is one zero between the decimal point and the first digit
not zero, we must set the indicator over 34 on the middle third of the K
scale. We read the result 324 on the D scale. The decimal point may be
placed as follows:

cube_root( .034 ) = cube_root( 34/1000 )
= 1/10 cube_root( 34 )

The nearest perfect cube to 34 is 27, so our answer must be close to
one-tenth of the cube root of 27 or nearly 0.3. Therefore, we must place
the decimal point to give 0.324. A group of examples for practice in
extraction of cube root follows:

Example
43: cube_root( 64 ) = 4
44: cube_root( 8 ) =