SHAKUNTALA   DEVI’S  WORK  IN  MATHS

Mental calculation

Shakuntala Devi travelled the world demonstrating her arithmetic talents, including a tour of Europe in 1950 and a performance in New York City in 1976. In 1988, she travelled to the US to have her abilities studied by Arthur Jensen, a professor of psychology at the University of California, Berkeley. Jensen tested her performance of several tasks, including the calculation of large numbers. Examples of the problems presented to Devi included calculating the cube root of 61,629,875 and the seventh root of 170,859,375. Jensen reported that Shakuntala Devi provided the solution to the above mentioned problems (395 and 15, respectively) before Jensen could copy them down in his notebook. Jensen published his findings in the academic journal Intelligence in 1990.

In 1977, at Southern Methodist University, she gave the 23rd root of a 201-digit number in 50 seconds. Her answer—546,372,891—was confirmed by calculations done at the US Bureau of Standards by the UNIVAC 1101 computer, for which a special program had to be written to perform such a large calculation.

On 18 June 1980, she demonstrated the multiplication of two 13-digit numbers—7,686,369,774,870 × 2,465,099,745,779—picked at random by the Computer Department of Imperial College London. She correctly answered 18,947,668,177,995,426,462,773,730 in 28 seconds. This event was recorded in the 1982 Guinness Book of Records. Writer Steven Smith said, "the result is so far superior to anything previously reported that it can only be described as unbelievable".

Shakuntala Devi explained many of the methods she used to do mental calculations in her book 'Figuring: The Joy of Numbers', that is still in print.