Lightning Calculators

The late Georgo Bidder, ut tlie ago of 8, could answer almost instantaneousiy liow many farthings there are in L868,424,121. Zerah Colburn was another "lightning calculator" of the same generation. Once he was asked to name the square of 999,999, which he stated to be 999,998,000,001. He multiplied this by 49, and the product by the snme numbèr, and the total result he then multiplied by 25. He raised the figure 8 to the sixteenth power with case. He named the squares of 244,999,755 and 1,224,998,755. He instantly named the factors, 941 and 2(13, whieh would produce 247,483. He eould diacover prime numbers almost as soon as namod. In flve seconds he calculated the cube root of 413,993,348,(177.