24. Feasibility of Two-hand Method
Sometimes, parents of left-handed students would want to know whether their children can learn abacus using their left hand to write and operate the abacus. Left-handed people make up a larger portion of the population of non-Chinese ethnicity. Possible factors include the unique features of Chinese calligraphy and that most Chinese parents teach their children to write with the right hand. Using both hands is beneficial to learning for students. Some essays claim that left-handed children are more creative and smarter.
How does this apply to learn abacus and mental arithmetic?
Abacus's configuration is designed to accommodate the decimal system. The further on the left you go on the abacus will give you a bigger number. The further on the right you go will give you a smaller number. It is evident from the configuration that the abacus is designed for right-handed users. Some teachers think both hands are interchangeable, and students can decide on their own. There are a few considerations to be made here:
The formulae in the one-hand method correspond to the right-hand movement from left to right. The movements using the left hand are opposite of the formulae.
Holding the pen or pencil with the right hand will keep the force centralized in the palm. Holding the pen or pencil with the left hand will disperse the divide of the force between the fingers. What if students both hold the pen and calculate using the left hand? Since the calculation depends on the formulae, using the left hand still contradicts the formulae. For example, +1=-9+10 (using the 10’s complement addition formula) versus +1 = +10 -9 (opposite direction); -1= -10+9 (using the 10’s complement subtraction formula) versus -1 = +9-10 (opposite direction).
Using the left hand in the early stage is still feasible. However, once there are more digits, students will find it increasingly difficult to solve the questions, and they will become slower. This most likely happens when they advance to 4-digit addition and subtraction on the abacus, 6-digit multiplication, or 5-digit division onward.
In flip-file (banknote) practice, the left hand is traditionally used to turn the pages and support the notes, sometimes even support the abacus. The right hand is still used to calculate, and the two hands are already occupied. Students who use left-hand to operate the abacus will find flip-file especially difficult unless they calculate mentally.
If the students only plan to learn abacus and mental arithmetic for no more than three years and students have learned the basic calculation skills with the abacus, then the issue of using the left or right-hand does not matter.