644309 ÷ 81 
The aim is to understand the frequency of 81 in 644309.

On to step 1:
81 can be fit into 6 0 times, resulting in a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Take the next digit (4) from the dividend and append it to 6, then repeat: 64 / 81

On to step 2:
The number 81 fits into 64 0 times, leaving a remainder of 64.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 64 after subtracting 0 from 64.
Take the next digit (4) from the dividend and append it to 64, then repeat: 644 / 81

On to step 3:
The number 81 fits into 644 7 times, leaving a remainder of 77.
Record the quotient 7 as the next digit in the result. 
Result so far: 7.0
If we subtract 567 from 644, we get 77.
Fetch the next digit (3) from the dividend, attach it to 77 and continue: 773 / 81

On to step 4:
When dividing 773 by 81, we get 9 with a remainder of 44.
Put 9 as the next digit of the answer. 
Result so far: 79.0
Subtract 729 from 773 to get 44.
Append the next digit (0) from the dividend to 44 and continue with: 440 / 81

Step 5:
If we divide 440 by 81, we get 5 and a remainder of 35.
The next digit of our result is 5. 
Result so far: 795.0
The remainder is 35 after subtracting 405 from 440.
Take the next digit (9) from the dividend and append it to 35, then repeat: 359 / 81

Going ahead to step 6:
The number 81 fits into 359 4 times, leaving a remainder of 35.
Record the quotient 4 as the next digit in the result. 
Result so far: 7954.0
If we subtract 324 from 359, we get 35.
Since there are no more digits in the dividend, we add a zero to the remainder making it 350, and continue the process.

Let's proceed to step 7:
The number 81 fits into 350 4 times, leaving a remainder of 26.
The number 4 becomes the next digit in our result. 
Result so far: 7954.4
The remainder is 26 after subtracting 324 from 350.
Since there are no more digits in the dividend, we add a zero to the remainder making it 260, and continue the process.

Advancing to step 8:
The number 81 fits into 260 3 times, leaving a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 7954.43
Subtract 243 from 260 to get 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Going ahead to step 9:
81 goes into 170 2 times with a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 7954.432
Subtracting 162 from 170 leaves us with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 10:
When dividing 80 by 81, we get 0 with a remainder of 80.
Write down 0 as next digit of the result. 
Result so far: 7954.432
If we subtract 0 from 80, we get 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

Let's proceed to step 11:
800 divided by 81 is 9 with a remainder of 71.
The next digit of our result is 9. 
Result so far: 7954.43209
Subtracting 729 from 800 leaves us with 71.
Since there are no more digits in the dividend, we add a zero to the remainder making it 710, and continue the process.

Moving on to step 12:
81 can be fit into 710 8 times, resulting in a remainder of 62.
Put 8 as the next digit of the answer. 
Result so far: 7954.432098
Subtracting 648 from 710 leaves us with 62.
Since there are no more digits in the dividend, we add a zero to the remainder making it 620, and continue the process.

Going ahead to step 13:
If we divide 620 by 81, we get 7 and a remainder of 53.
Use 7 as the next digit of our solution. 
Result so far: 7954.4320987
Subtract 567 from 620 to get 53.
Since there are no more digits in the dividend, we add a zero to the remainder making it 530, and continue the process.

Moving on to step 14:
81 can be fit into 530 6 times, resulting in a remainder of 44.
The number 6 becomes the next digit in our result. 
Result so far: 7954.43209876
Subtract 486 from 530 to get 44.
Since there are no more digits in the dividend, we add a zero to the remainder making it 440, and continue the process.

The quotient of the division is 7954.43209876, and the remainder is 4.4e-08.