We're dividing 816689 by 90 
The aim is to understand the frequency of 90 in 816689.

Let's proceed to step 1:
The number 90 fits into 8 0 times, leaving a remainder of 8.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 8, we end up with 8.
Fetch the next digit (1) from the dividend, attach it to 8 and continue: 81 / 90

On to step 2:
The number 90 fits into 81 0 times, leaving a remainder of 81.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 81, we end up with 81.
Grab the next digit (6) from the dividend, add it to 81, then carry on: 816 / 90

Let's proceed to step 3:
When dividing 816 by 90, we get 9 with a remainder of 6.
Write down 9 as next digit of the result. 
Result so far: 9.0
The remainder is 6 after subtracting 810 from 816.
Bring next digit (6) of the dividend behind the 6 and repeat the process: 66 / 90

On to step 4:
If we divide 66 by 90, we get 0 and a remainder of 66.
Record the quotient 0 as the next digit in the result. 
Result so far: 90.0
Subtracting 0 from 66 leaves us with 66.
Include the next digit (8) from the dividend after 66, then repeat: 668 / 90

Advancing to step 5:
When dividing 668 by 90, we get 7 with a remainder of 38.
Use 7 as the next digit of our solution. 
Result so far: 907.0
If we subtract 630 from 668, we get 38.
Grab the next digit (9) from the dividend, add it to 38, then carry on: 389 / 90

Going ahead to step 6:
90 can be fit into 389 4 times, resulting in a remainder of 29.
Record the quotient 4 as the next digit in the result. 
Result so far: 9074.0
If we take 360 away from 389, we end up with 29.
Since there are no more digits in the dividend, we add a zero to the remainder making it 290, and continue the process.

Step 7:
When dividing 290 by 90, we get 3 with a remainder of 20.
Use 3 as the next digit of our solution. 
Result so far: 9074.3
Subtracting 270 from 290 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 8:
If we divide 200 by 90, we get 2 and a remainder of 20.
Record the quotient 2 as the next digit in the result. 
Result so far: 9074.32
Deduct 180 from 200 and we're left with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 9:
90 can be fit into 200 2 times, resulting in a remainder of 20.
The number 2 becomes the next digit in our result. 
Result so far: 9074.322
Subtracting 180 from 200 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

The final outcome is 9074.322, with a leftover of 0.002.