Before multiplication and division can be explained, it is
necessary to know a little more about the calculator. Firstly,
the figure wheels of the output register and their associated
transfer gears and carry cams are mounted on a movable carriage
which can be shifted to the left or to the right. In the
illustration it has been shifted six places to the left. There is
a movable pointer just below register two which indicates which
column of figures is active (in this case, column six).
Secondly, register two, on the upper right of the machine, will increment the active column (and if necessary carry to the left) each time the crank handle completes one rotation.
Having got that over with, we can proceed and think about multiplying 456 by 123.
One way of doing this is to enter 456 on the setting levers and then turn the handle one hundred and twenty three times. This is the sort of thing that people used to do when they got bored but there is an easier way.
456 000000003 ^ 000000000000001368
456 000000023 ^ 000000000000010488
456 000000123 ^ 000000000000056088
Division is accomplished by repeated subtractions, but the nice thing about division is that there is a little bell that rings every so often during the calculation.
We are going to divide 456 by 123
456 100000000 ^ 000000045600000000
000 000000000 ^ 000000045600000000
123 100000000 ^ 000000033300000000
123 200000000 ^ 000000021000000000
123 300000000 ^ 000000008700000000
123 400000000 ^ 999999996400000000 (ping!!) - Warning - we have gone too far
123 300000000 ^ 000000008700000000
123 300000000 ^ 000000008700000000
123 310000000 ^ 000000007470000000
123 380000000 ^ 999999998860000000 (ping!!)
123 370000000 ^ 000000000090000000
123 370000000 ^ 000000000090000000
123 370000000 ^ 000000000090000000
123 370700000 ^ 000000000003900000
123 370700000 ^ 000000000003900000
123 370730000 ^ 000000000000210000
And so on....
The result is 3.7073... (the decimal place has to be worked out by inspection)
..... and you would not believe just how fast some people
could do calculations like this.