5. Multiplication. The process of multiplication may be performed by using scales C and D. The C scale is on the slide, but in other respects it is like the D scale and is read in the same manner.
To multiply 2 by 4,
to 2 on D set index of C,
push hairline to 4 on C,
at the hairline read 8 on D.
Fig. 5 shows the rule in skeleton form set for multiplying 2 by 4.
To multiply 3 × 3,
to 3 on D set index of C,
push hairline to 3 on C,
at the hairline read 9 on D.
See Fig. 6 for the setting in skeleton form.
To Multiply 1.5 × 3.5, disregard the decimal point and
to 15 on D set index of C,
push hairline to 35 on C,
at the hairline read 525 on D.
By inspection we know that the answer is near to 5 and is therefore 5.25.
To find the value of 16.75 × 2.83 (see Fig. 7).
disregard the decimal point and
to 1675 on D set index of C,
push hairline to 283 on C,
at the hairline read 474 on D.
To place the decimal point we approximate the answer by noting that it is near to 3 × 16 = 48. Hence the answer is 47.4.
To find the value of 0.001753 × 12.17,
to 1753 on D set left index of C,
push hairline to 1217 on C,
at the hairline read 2135 on D.
To place the decimal point, approximate the answer by writing .002 × 10 = .02. Hence the answer is 0.02135.
These examples illustrate the use of the following rule.
Rule. To find the product of two numbers, disregard the decimal points, opposite either of the numbers on the D scale set the index of the C scale, push the hairline of the indicator to the second number on the C scale, and read the answer under the hairline of the D scale. The decimal point is placed in accordance with the result of a rough calculation.
3 × 2.
