Common Fractions.
As in commercial computations common fractions very often occur the most convenient method of multiplying a whole number by a fraction on the Comptometer is given below.
To Multiply a Whole Number by a Fraction. Multiply the whole number by the numerator first. As the product will then be indicated on the register, it can be divided by the denominator; and after pointing off the quotient, the remainder, if any, will constitute a new numerator.
Example: Find the value of 436 multiplied by 4⁄7. After multiplying 436 by 4, 1744 appears on the register. Now divide this amount by 7, and 249 appears as quotient, and 1 as remainder. Ans. 2491⁄7.
To Multiply a Whole Number by a Mixed Number. First multiply by the numerator of the mixed number, and then dividing by the denominator and leaving the result standing on the register, consider the units column of the quotient as the units column on the machine, and multiply by the integral part of the mixed number.
Thus: what is the product of 453 multiplied by 3725⁄16? After multiplying by the numerator, 5, 2265 appears, which being divided by 16, the denominator, 1419⁄16, is the result. As there are two places in the denominator, we ignore the first two columns of the machine and consider the third column as the units or first column, and multiplying by 372, the result, 168,6579⁄16, appears on the register.
