For certain classes of examples in multiplication short methods may be
employed and the labor of calculation reduced, but of course for the
great bulk of multiplications no practical abbreviation remains. A
person having much multiplying to do should learn the table up to
twenty, which can be done without much labor.
To multiply any number by 10, 100, or 1000, simply annex one, two, or
three ciphers, as the case may be. If it is desired to multiply by
20, 300, 5000, or a number greater than one with any number of ciphers
annexed, multiply first by the number and then annex as many ciphers
as the multiplier contains.