643635 ÷ 31 
The aim is to understand the frequency of 31 in 643635.

On to step 1:
If we divide 6 by 31, we get 0 and a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Grab the next digit (4) from the dividend, add it to 6, then carry on: 64 / 31

Advancing to step 2:
If we divide 64 by 31, we get 2 and a remainder of 2.
The number 2 becomes the next digit in our result. 
Result so far: 2.0
If we take 62 away from 64, we end up with 2.
Append the next digit (3) from the dividend to 2 and continue with: 23 / 31

On to step 3:
23 divided by 31 is 0 with a remainder of 23.
Use 0 as the next digit of our solution. 
Result so far: 20.0
If we take 0 away from 23, we end up with 23.
Bring next digit (6) of the dividend behind the 23 and repeat the process: 236 / 31

Let's proceed to step 4:
31 goes into 236 7 times with a remainder of 19.
Write down 7 as next digit of the result. 
Result so far: 207.0
Subtract 217 from 236 to get 19.
Bring next digit (3) of the dividend behind the 19 and repeat the process: 193 / 31

Let's proceed to step 5:
31 goes into 193 6 times with a remainder of 7.
The number 6 becomes the next digit in our result. 
Result so far: 2076.0
If we subtract 186 from 193, we get 7.
Grab the next digit (5) from the dividend, add it to 7, then carry on: 75 / 31

Going ahead to step 6:
31 can be fit into 75 2 times, resulting in a remainder of 13.
The number 2 becomes the next digit in our result. 
Result so far: 20762.0
Deduct 62 from 75 and we're left with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 7:
If we divide 130 by 31, we get 4 and a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 20762.4
If we subtract 124 from 130, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 8:
When dividing 60 by 31, we get 1 with a remainder of 29.
The next digit of our result is 1. 
Result so far: 20762.41
The remainder is 29 after subtracting 31 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 290, and continue the process.

On to step 9:
If we divide 290 by 31, we get 9 and a remainder of 11.
Write down 9 as next digit of the result. 
Result so far: 20762.419
Subtract 279 from 290 to get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Advancing to step 10:
31 goes into 110 3 times with a remainder of 17.
The number 3 becomes the next digit in our result. 
Result so far: 20762.4193
The remainder is 17 after subtracting 93 from 110.
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 11:
The number 31 fits into 170 5 times, leaving a remainder of 15.
Use 5 as the next digit of our solution. 
Result so far: 20762.41935
Subtracting 155 from 170 leaves us with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 12:
If we divide 150 by 31, we get 4 and a remainder of 26.
Record the quotient 4 as the next digit in the result. 
Result so far: 20762.419354
If we take 124 away from 150, we end up with 26.
Since there are no more digits in the dividend, we add a zero to the remainder making it 260, and continue the process.

Let's proceed to step 13:
31 can be fit into 260 8 times, resulting in a remainder of 12.
The next digit of our result is 8. 
Result so far: 20762.4193548
Deduct 248 from 260 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Advancing to step 14:
When dividing 120 by 31, we get 3 with a remainder of 27.
Record the quotient 3 as the next digit in the result. 
Result so far: 20762.41935483
Deduct 93 from 120 and we're left with 27.
Since there are no more digits in the dividend, we add a zero to the remainder making it 270, and continue the process.

After the division, we end up with 20762.41935483 and a remainder of 2.7e-08.