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Chisanbop or chisenbop (from Korean chi (ji) finger + sanpŏp (sanbeop) calculation 지산법/指算法) is an abacus-like finger counting method used to perform basic mathematical operations. According to The Complete Book of Chisanbop by Hang Young Pai, chisanbop was created in the 1940s in Korea by Sung Jin Pai and revised by his son Hang Young Pai. He then brought the system to the United States circa 1977. With this method it is possible to display all numbers from 0 to 99 with two hands.
The hands are held in a relaxed posture on or above a table. All fingers are floating off the table to begin with. The fingers are pressed into the table to indicate value. Each finger (but not the thumb) of the right hand has a value of one. Press the index finger of the right hand onto the table to indicate "one." Press the index and middle fingers for “two”, the three leftmost fingers for “three”, and all four fingers of the right hand to indicate “four”. The thumb of the right hand holds the value “five”. To place the value “six”, press the right thumb and index finger onto the table. The thumb indicates “five” plus the “one” indicated by the finger. The left hand represents the tens digit. It works like the right hand, but each value is multiplied by ten. Each finger on the left hand represents “ten”, and the left thumb represents “fifty”. In this way, all values between zero and ninety-nine can be indicated on two hands.
A proposed notation system for representing the numbers:
. = a finger off the table o = a finger on the table - = a thumb off the table @ = a thumb on the table
Values between zero and 9 are shown with the entire right hand:
@oooo = 9 @ooo. = 8 @oo.. = 7 @o... = 6 @.... = 5 -oooo = 4 -ooo. = 3 -oo.. = 2 -o... = 1 -.... = 0
Values larger than 10 are shown with both hands:
..oo- @.... = 25 ....@ @.... = 55 oooo- -.... = 40