We look at the division of 511820 by 90 
The aim is to understand the frequency of 90 in 511820.

On to step 1:
The number 90 fits into 5 0 times, leaving a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 5 after subtracting 0 from 5.
Take the next digit (1) from the dividend and append it to 5, then repeat: 51 / 90

Step 2:
90 can be fit into 51 0 times, resulting in a remainder of 51.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 51 and we're left with 51.
Bring next digit (1) of the dividend behind the 51 and repeat the process: 511 / 90

Going ahead to step 3:
90 can be fit into 511 5 times, resulting in a remainder of 61.
Put 5 as the next digit of the answer. 
Result so far: 5.0
If we subtract 450 from 511, we get 61.
Fetch the next digit (8) from the dividend, attach it to 61 and continue: 618 / 90

Let's proceed to step 4:
The number 90 fits into 618 6 times, leaving a remainder of 78.
Put 6 as the next digit of the answer. 
Result so far: 56.0
Subtract 540 from 618 to get 78.
Bring next digit (2) of the dividend behind the 78 and repeat the process: 782 / 90

Going ahead to step 5:
The number 90 fits into 782 8 times, leaving a remainder of 62.
The next digit of our result is 8. 
Result so far: 568.0
Deduct 720 from 782 and we're left with 62.
Take the next digit (0) from the dividend and append it to 62, then repeat: 620 / 90

Moving on to step 6:
When dividing 620 by 90, we get 6 with a remainder of 80.
Record the quotient 6 as the next digit in the result. 
Result so far: 5686.0
Subtract 540 from 620 to 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.

Moving on to step 7:
90 goes into 800 8 times with a remainder of 80.
Use 8 as the next digit of our solution. 
Result so far: 5686.8
If we take 720 away from 800, we end up with 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

Step 8:
90 can be fit into 800 8 times, resulting in a remainder of 80.
The number 8 becomes the next digit in our result. 
Result so far: 5686.88
Subtracting 720 from 800 leaves us with 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

The final outcome is 5686.88, with a leftover of 0.08.