There is still a time in memory when the simplest calculators were a luxury, and there was no talk of computers. Sellers, postal workers, and even bank clerks used accounts.

## Instructions

### Step 1

Abacus is the simplest computing device, which is a counting ring strung on thin knitting needles. Framed by a single canvas, abacus contains the entire system of numbers - ones, tens, hundreds, etc. On the top rows of the count are integers, and their value decreases with each next spoke: from hundreds of thousands to units. Fractional numbers are located under a short row of "knuckles": from tenths to thousandths.

### Step 2

The simplest calculations in accounts are addition and subtraction. The numbers are typed starting from the first row of integers: from 1 to 10. The next rad (one spoke up) - from 11 to 20, etc. Dial the required number by moving the "knuckles" from the corresponding row from right to left. When one row on the spoke is full, use the larger numbers - that is, one “knuckle” of the top row replaces 10 “knuckles” of the lower one. As you add up the numbers, add the "knuckles" to the corresponding rows. To calculate the final result, "go down" down to the top - millions, thousands, hundreds, etc.

### Step 3

Subtraction on accounts is performed in the same way as addition, only in reverse order. That is, subtracting another from one number, remove the "knuckles" from the corresponding rows. Thus, while counting, move from top to bottom. You will find out the final amount by counting the rings remaining on the left side of the account.

### Step 4

For each number, multiplication on accounts is done in different ways. If you need to multiply by 2 or 3, replace this action with addition, "plus" the number 2 or 3 times, respectively. Multiplication by 4 is addition (2 * 2).

### Step 5

To multiply by 5, move all the tiles up one line (that is, multiply it by 10), then divide the number in half in your head.

### Step 6

To multiply a number by 6, you need to multiply it by 5 in the way described above, then add the number that was at the beginning of the calculations to the result.

### Step 7

To multiply by 7, first multiply the number by 10, and then subtract the number to be multiplied three times from the resulting value.

### Step 8

Multiplication by 8 or 9 is replaced by multiplication by 10, but without carrying 2x or 1st (when multiplied by 8 and 9, respectively) bones up.

### Step 9

The factors that follow after 10 are "decomposed" into components. For example, you need to multiply by 12 - you are expanding this factor by 10 and 2. Add the number to yourself (multiply by 2), then add the tenfold value to it.

### Step 10

Account division is a complex process that is accessible only to professionals. In the old days, it was necessary to undergo special training in order to master the division.