In this example, we consider the combined operations of multiplication and division. As you will see, most of the steps are the same.

Step 1:
Using the front of the slide rule (like any other slide rule), we calculate the significant figures of the problem (45 x 735) ÷ (86 x 254) arriving at the digits 151.

Step 2:
On the back of the slider, perform the same calculation using the condensed C and D scales (C' and D') on the right. We find that the result falls in region 0 (zero). The calculation is started at the left and since the D' index goes off scale, the calculation continues on the right. Admittedly, this will depend on how you perform the continued operations, but the result will still fall in the zero region.

Step 3:
Align the inverted triangle above the 0 (zero) on the RN-DZ scale.

Step 4:
Now we determine the requirements for the difference number (DN). SInce we have both numerator and denominator, we need to complete two calculations.

Numerator ...

1. Count the number of factors, F. In this case 2, i.e. from 0.0045 x 735.
2. The number of zeros, Z. In this case 3, i.e. from 0.00045
3. The number of digits, D. In this case 3, i.e. from 765.

Denominator ...

1. Count the number of factors, F. In this case 2, i.e. from 86000 x 0.000254.
2. The number of zeros, Z. In this case 3, i.e. from 0.000254.
3. The number of digits, D. In this case 5, i.e. from 86000.

Step 5:
Calculate the difference number (DN).

Numerator ... D - (F + Z) = 3 - (2 + 3) = -2
Denominator ... D - (F + Z) = 5 - (2 + 3) = 0

The difference number (DN) is calculated by subtracting the denominator value from the numerator value:

-2 - 0 = -2

Step 6:
Below -2 on the DN scale, we locate -1 on the RN-DZ scale. Note that the slider has not been moved since the inverted arrow was aligned with 0 (zero) on the RN-DZ scale, step 3.

This value means that the result has 1 (one) zero behind the decimal point. Hence 0.0151 is the answer to our calculation.

   Proceed to Square Root Example