We look at the division of 612288 by 31 
The aim is to understand the frequency of 31 in 612288.

On to step 1:
If we divide 6 by 31, we get 0 and a remainder of 6.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Fetch the next digit (1) from the dividend, attach it to 6 and continue: 61 / 31

Moving on to step 2:
31 can be fit into 61 1 times, resulting in a remainder of 30.
The next digit of our result is 1. 
Result so far: 1.0
Deduct 31 from 61 and we're left with 30.
Include the next digit (2) from the dividend after 30, then repeat: 302 / 31

Step 3:
When dividing 302 by 31, we get 9 with a remainder of 23.
Use 9 as the next digit of our solution. 
Result so far: 19.0
Subtracting 279 from 302 leaves us with 23.
Fetch the next digit (2) from the dividend, attach it to 23 and continue: 232 / 31

Advancing to step 4:
31 goes into 232 7 times with a remainder of 15.
The next digit of our result is 7. 
Result so far: 197.0
Subtracting 217 from 232 leaves us with 15.
Bring next digit (8) of the dividend behind the 15 and repeat the process: 158 / 31

Let's proceed to step 5:
The number 31 fits into 158 5 times, leaving a remainder of 3.
Put 5 as the next digit of the answer. 
Result so far: 1975.0
If we subtract 155 from 158, we get 3.
Fetch the next digit (8) from the dividend, attach it to 3 and continue: 38 / 31

Going ahead to step 6:
If we divide 38 by 31, we get 1 and a remainder of 7.
Write down 1 as next digit of the result. 
Result so far: 19751.0
Subtracting 31 from 38 leaves us with 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Moving on to step 7:
The number 31 fits into 70 2 times, leaving a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 19751.2
Subtracting 62 from 70 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.

On to step 8:
31 goes into 80 2 times with a remainder of 18.
The next digit of our result is 2. 
Result so far: 19751.22
Subtract 62 from 80 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

The final result is 19751.22 with a remainder of 0.018.