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Trachtenberg defined this algorithm with a kind of pairwise multiplication where two digits are multiplied by one digit, essentially only keeping the middle digit of the result. By performing the above algorithm with this pairwise multiplication, even fewer temporary results need to be held. Example:
The abacus system of mental calculation is a system where users mentally visualize an abacus to carry out arithmetical calculations. [1] No physical abacus is used; only the answers are written down. Calculations can be made at great speed in this way.
The number that is two times the simple is marked in the two triangles marked × 2. If the number is two digits, the first digit is placed to the left of the main diagonal (marked in red) and the second digit to the right of the diagonal. If the number is a single digit, it is marked to the right of the diagonal; The number that is 3 times the ...
36 represented in chisanbop, where four fingers and a thumb are touching the table and the rest of the digits are raised. The three fingers on the left hand represent 10+10+10 = 30; the thumb and one finger on the right hand represent 5+1=6. Counting from 1 to 20 in Chisanbop. Each finger has a value of one, while the thumb has a value of five.
If one has a two-digit number, take it and add the two numbers together and put that sum in the middle, and one can get the answer. For example: 24 x 11 = 264 because 2 + 4 = 6 and the 6 is placed in between the 2 and the 4.
In arbitrary-precision arithmetic, it is common to use long multiplication with the base set to 2 w, where w is the number of bits in a word, for multiplying relatively small numbers. To multiply two numbers with n digits using this method, one needs about n 2 operations.
A suanpan (top) and a soroban (bottom). The two abaci seen here are of standard size and have thirteen rods each. Another variant of soroban. The soroban is composed of an odd number of columns or rods, each having beads: one separate bead having a value of five, called go-dama (五玉, ごだま, "five-bead") and four beads each having a value of one, called ichi-dama (一玉, いちだま ...
The Korean finger counting system Chisanbop uses a bi-quinary system, where each finger represents a one and a thumb represents a five, allowing one to count from 0 to 99 with two hands. One advantage of one bi-quinary encoding scheme on digital computers is that it must have two bits set (one in the binary field and one in the quinary field ...