Hi everyone, this is my first post where in I will try to explain the basics of 'Soroban'. My first post was originally supposed to be on computer networking but soroban is something which has made me immensely curious at present. So, the source of my information is largely from my 12 years younger sister, I'm 22. Apart from that I will explain the basics of soroban which I went on to collect from various other sources and will combine them in simple format here. So I'll post more as and when my sister progress in her class.
Contents : 1. What is Soroban ?
2. Counting on Soroban.
3. Addition at same place value.
4. Addition from next place value.
Lets Begin. . .
1. What is Soroban ?
Soroban is an abacus developed in Japan. Its the Japanese version of ancient computing device know as the abacus and hence also called Japanese Abacus. It also has Indian, Chinese, Korean and many more versions. Its interesting that sorobans are used even today as calculation devices.
2. Counting on Soroban.
A soroban consists of rows of bicone shaped beads and has odd number of such rods. Each rod has two types of beads seperated by a bar called reckoning bar. The single bead above this bar is called heavenly bead and the ones below it is called earth beads. The heavenly beads hold a value of five and the earth beads has value of one each. Now, when it comes to number of beads per rod, it differs for different versions of abacus. The closest chinese version has two heavenly beads instead of one in soroban and five earth beads compared to four of soroban.
Now every rod in the device has a place value like the place value chart of a number system. A white dot above a rod called unit dot indicates its a unit rod. Every third rod is a unit rod and the rod to the left of it is tens, then hundreds, thousands and so on. Similarly, the rods to the left hold the decimal values with some exceptions during division and multiplication calculation.
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| Soroban Japanese Abacus |
To explain counting on soroban, I have named a few rods with their relevant place values and beads with the values it would take when moved towards the reckoning bar. Now let me make it clear that those are not the values of the beads itself but are the values they would take at that specific place value when moved towards the reckoning bar. The value of every earth beads nd heavenly beads are one and five respectively.
When all beads on device are away from the reckoning bar, the device is said to be in its initial state or reset, the device is not indicating any value on it. The heavenly bead and earth beads are moved using index finger and thumb finger respectively. When the first earth bead at unit place is moved up, it forms one. The device is now said to show 1 as the value on it. For two, the next bead at unit place is moved. The earth beads at unit place can form a maximum value of four when all four beads are moved up. Hence for five we have a heavenly bead whose value is also 5. Hence five is indicated by moving the heavenly bead at unit place down. Note at this point all the earth beads go back to original positions because the value of single heavenly bead is itself five. For values from six to nine, the earth beads at the units place is also moved up one by one and hence adds up with five of heavenly bead to give numbers till 9.
Now, all the beads togather at unit place can make values upto 9. Ten can be obtained by moving the first earth bead at tens place towards the reckoning bar. Here all beads at ones place are reset. Now for eleven, the first earth bead at unit place can be moved up towards the reckoning bar because we know that its value is one and hence it makes eleven along with 10. Similarly for twelve the next bead in unit place is moved up and the process continues by moving beads at various place values towards the reckoning bar to make combinations of numbers.
The basic counting process of soroban could have been better demonstrated by a video which I'm looking forward to in future posts. For the time being I'll post some photos with various bead positions for better understanding in the very next post.
