The mental calculation speed rapidly becomes early by putting the abacus in the head.
This software is an application program that sequentially adds ten figures that appear one after another, and becomes familiar with the abacus.
The level of the sense from the digit number and 3 seconds from 1 digit to the treble to 1 seconds is prepared. Where can you calculate?
The mental calculation mode is prepared of course, and calculate with an abacus in the head, please. The mental calculation of the flash of the treble is not a dream.