We're dividing 621235 by 90 
The aim is to understand the frequency of 90 in 621235.

Let's proceed to step 1:
When dividing 6 by 90, we get 0 with a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 6 leaves us with 6.
Append the next digit (2) from the dividend to 6 and continue with: 62 / 90

Let's proceed to step 2:
When dividing 62 by 90, we get 0 with a remainder of 62.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 62 after subtracting 0 from 62.
Fetch the next digit (1) from the dividend, attach it to 62 and continue: 621 / 90

Moving on to step 3:
If we divide 621 by 90, we get 6 and a remainder of 81.
Use 6 as the next digit of our solution. 
Result so far: 6.0
Deduct 540 from 621 and we're left with 81.
Grab the next digit (2) from the dividend, add it to 81, then carry on: 812 / 90

Going ahead to step 4:
90 goes into 812 9 times with a remainder of 2.
The next digit of our result is 9. 
Result so far: 69.0
If we subtract 810 from 812, we get 2.
Append the next digit (3) from the dividend to 2 and continue with: 23 / 90

Moving on to step 5:
The number 90 fits into 23 0 times, leaving a remainder of 23.
The next digit of our result is 0. 
Result so far: 690.0
Subtracting 0 from 23 leaves us with 23.
Include the next digit (5) from the dividend after 23, then repeat: 235 / 90

Let's proceed to step 6:
235 divided by 90 is 2 with a remainder of 55.
Record the quotient 2 as the next digit in the result. 
Result so far: 6902.0
Subtracting 180 from 235 leaves us with 55.
Since there are no more digits in the dividend, we add a zero to the remainder making it 550, and continue the process.

Going ahead to step 7:
90 can be fit into 550 6 times, resulting in a remainder of 10.
The next digit of our result is 6. 
Result so far: 6902.6
If we subtract 540 from 550, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Let's proceed to step 8:
90 can be fit into 100 1 times, resulting in a remainder of 10.
Record the quotient 1 as the next digit in the result. 
Result so far: 6902.61
Deduct 90 from 100 and we're left with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Advancing to step 9:
90 goes into 100 1 times with a remainder of 10.
The number 1 becomes the next digit in our result. 
Result so far: 6902.611
If we subtract 90 from 100, we get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

The final result is 6902.611 with a remainder of 0.001.