Chisanbop is useful in recalling numbers needed in the midst of calculating.
When doing mental calculations, I don’t want a number to disappear in the midst of problem steps. Often I find it helpful to use an abacus-like Korean method called Chisanbop to register a number up to 99 on my fingers. The utility of using Chisanbop for number operations is debatable, but the tactile sensation of the fingers registering a number helps in remembering it. Here I describe the method, and you can try it for yourself. If nothing else, you can use it to interest people showing them how you can count to 99 on your fingers.
Disregard the method of counting fingers in piano which is thumb-pinky 1,2,3,4,5. In Chisanbop the counting goes index-pinky 1,2,3,4, pressing and feeling all fingers on the palm up to the number being registered for best effect. The thumb by itself is 5. Touching thumb to index is 5+1, thumb to index+middle is 5+2 …touching thumb to pinky is 5+4. Do the units digits 1,2,3,4,5,6,7,8,9 on the right hand, saving the left hand to register the tens digits.
On the left hand the counting is in tens, not units, but works the same way. The index finger pressed down is 10… all fingers including the pinky is 40. The thumb is 50. The thumb with index and middle fingers pressed to it is 70. The thumb and all fingers including pinky pressed to it is 90.
Using both hands, registering any number up to 99 is easy: register the tens on the left hand and the units on the right. If you want to register hundreds, do what is comfortable and workable for you. You may try pressing toes for 100 and 200.
