We look at the division of 810868 by 90 
The aim is to understand the frequency of 90 in 810868.

Step 1:
90 can be fit into 8 0 times, resulting in a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 8 to get 8.
Fetch the next digit (1) from the dividend, attach it to 8 and continue: 81 / 90

Moving on to step 2:
81 divided by 90 is 0 with a remainder of 81.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtract 0 from 81 to get 81.
Append the next digit (0) from the dividend to 81 and continue with: 810 / 90

Moving on to step 3:
When dividing 810 by 90, we get 9 with a remainder of 0.
The next digit of our result is 9. 
Result so far: 9.0
If we subtract 810 from 810, we get 0.
Bring next digit (8) of the dividend behind the 0 and repeat the process: 8 / 90

On to step 4:
90 goes into 8 0 times with a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 90.0
If we subtract 0 from 8, we get 8.
Fetch the next digit (6) from the dividend, attach it to 8 and continue: 86 / 90

Moving on to step 5:
When dividing 86 by 90, we get 0 with a remainder of 86.
Record the quotient 0 as the next digit in the result. 
Result so far: 900.0
Deduct 0 from 86 and we're left with 86.
Fetch the next digit (8) from the dividend, attach it to 86 and continue: 868 / 90

Let's proceed to step 6:
When dividing 868 by 90, we get 9 with a remainder of 58.
Put 9 as the next digit of the answer. 
Result so far: 9009.0
The remainder is 58 after subtracting 810 from 868.
Since there are no more digits in the dividend, we add a zero to the remainder making it 580, and continue the process.

On to step 7:
90 goes into 580 6 times with a remainder of 40.
Record the quotient 6 as the next digit in the result. 
Result so far: 9009.6
The remainder is 40 after subtracting 540 from 580.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 8:
The number 90 fits into 400 4 times, leaving a remainder of 40.
The number 4 becomes the next digit in our result. 
Result so far: 9009.64
If we subtract 360 from 400, we get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

On to step 9:
90 goes into 400 4 times with a remainder of 40.
Put 4 as the next digit of the answer. 
Result so far: 9009.644
Deduct 360 from 400 and we're left with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

The final result is 9009.644 with a remainder of 0.004.