All in your head!
The ability to perform a complex calculation mentally, in an instant, is often associated with the idea of a "gift for numbers". It is true that some mental calculation prodigies seem to possess this quality without having received any particular training. However, one must not be fooled: apart from a few cases as rare as they are fascinating, the aptitude for mental calculation develops above all through practice. This produces all the more results as it is based on a good knowledge of the underlying properties of numbers, generally founded on a mixture of algebra and arithmetic.
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Mental arithmetic: first steps | Tangente
A few tricks can make mental arithmetic more efficient
Éric Trouillot: Mental arithmetic, a path to jubilation | Tangente
The inventor of the calculation game Mathador, Éric Trouillot is one of those working to bring mental arithmetic back into teaching practice. In his view, far from being tricks performed by trained monkeys, techniques for calculating in one's head are an excellent gateway into the world of numbers, as well as an irreplaceable way to put mathematical properties — such as the distributivity of multiplication — into concrete practice.
Calculating prodigies
Calculating prodigies fascinate the public with their ease in rapidly performing operations on large numbers. The tricks used by these number magicians draw on abilities that are more mnemonic than mathematical, but also on numerous methods and stratagems based on various theorems.
Divisibility in 19th-century textbooks | Tangente
Divisibility rules are numerous and are used by everyone who practises mental arithmetic. Blending arithmetic with common sense, they are a source of countless mathematical recreations, and have long been used in teaching.
Is this number prime?
Prime numbers form the backbone of arithmetic. Although their distribution remains a subject of cutting-edge research, being able to decide mentally whether a number is prime is an excellent mental exercise—both enjoyable and creative.
Number sense — A history of mental arithmetic | Tangente
For a time, electronic tools seemed to have consigned mental arithmetic to history. Yet in recent years it has made a strong comeback among educational priorities. Far from being merely a set of automatic procedures, mental arithmetic is an irreplaceable way to explore numerical structures and deepen our understanding of certain concepts.
What day will Doomsday fall on? | Tangente
A classic mentalist trick is to work out instantly, in their head, which day of the week corresponds to a given date. How do they know at once that January 27, 1962, was a Saturday? Here are some of the methods they use for our Gregorian calendar.