Multiplying

Press, Volume CII, Issue 30325, 28 December 1963, Page 3

Multiplying

Instant Maths. By Ann Cutler Souvenir Press 60 PP. During the years he spent in Hitler’s concentration camps as a political prisoner, an engineer named Jackow Trachtenberg spent his time in devising short cits in mathematics. In this little book Ann Cutler describes his methods of multiplying without having to depend on the multiplication tables, 2 to 12 times.

Everybody knows that if you wish to multiply a number by 10 you simply add a 0 at the end. If you time yourself and find out how long it takes to go through the normal process of multiplying each of the digits in e multi-digit number like 837 t by 10, you can calculate how much time you have been saved by knowing just to add the 0 to 8376. Professor Trachtenberg has devised schemes for each of the other multipliers, from 7 to 12. Each multiplier requires knowledge of a special method. The simplest to handle as multipliers are the numbers 11 and 12, and with a little practise you can soon multiply huge numbers as fast as a computing machine and into the bargain write the answers down backwards, from right to left. The basic rules for multiplying by 6 and 7 are a little more complicated, and the rules for multiplying by 9 or P or 4. though not hard to remember. take even more time to apply. Trachtenberg’s method of multiplying by 3. however, is hardly worth the bother of using—for surely everybody knows his three ■ times table, and it is just as quick to use this table as it is to use Trachtenberg’s device.

As a whole this new system of multiplying is ingenious and full of interest whether you are a mather atician or not The amateur conjuror, for instance, will be able to add much exciting fun to his performance by memorising the methods described in this short book of number tricks.

In the last few pages, for good measure. Ann Cutler also explains how to add up columns of numbers as long as your arm, and get the answer correctly in a few seconds. Before the introduction of adding machines this method (or a modification of it) was widely used by the bank clerk of by-gone days in totting up his ledgers. Learning the steps in "Instant Maths” is no harder than learning the rules of a new game. A master of these mathematical tricks will surprise the reader—and amaze his friends.