809139 divided by 90 
The aim is to understand the frequency of 90 in 809139.

Step 1:
When dividing 8 by 90, we get 0 with a remainder of 8.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 8 after subtracting 0 from 8.
Append the next digit (0) from the dividend to 8 and continue with: 80 / 90

Advancing to step 2:
80 divided by 90 is 0 with a remainder of 80.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 80 leaves us with 80.
Include the next digit (9) from the dividend after 80, then repeat: 809 / 90

Going ahead to step 3:
If we divide 809 by 90, we get 8 and a remainder of 89.
The next digit of our result is 8. 
Result so far: 8.0
If we take 720 away from 809, we end up with 89.
Take the next digit (1) from the dividend and append it to 89, then repeat: 891 / 90

Advancing to step 4:
When dividing 891 by 90, we get 9 with a remainder of 81.
Record the quotient 9 as the next digit in the result. 
Result so far: 89.0
If we take 810 away from 891, we end up with 81.
Grab the next digit (3) from the dividend, add it to 81, then carry on: 813 / 90

On to step 5:
90 goes into 813 9 times with a remainder of 3.
Use 9 as the next digit of our solution. 
Result so far: 899.0
Subtract 810 from 813 to get 3.
Fetch the next digit (9) from the dividend, attach it to 3 and continue: 39 / 90

On to step 6:
When dividing 39 by 90, we get 0 with a remainder of 39.
Write down 0 as next digit of the result. 
Result so far: 8990.0
Subtracting 0 from 39 leaves us with 39.
Since there are no more digits in the dividend, we add a zero to the remainder making it 390, and continue the process.

On to step 7:
If we divide 390 by 90, we get 4 and a remainder of 30.
Put 4 as the next digit of the answer. 
Result so far: 8990.4
If we subtract 360 from 390, we get 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Going ahead to step 8:
The number 90 fits into 300 3 times, leaving a remainder of 30.
The number 3 becomes the next digit in our result. 
Result so far: 8990.43
If we take 270 away from 300, we end up with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Advancing to step 9:
When dividing 300 by 90, we get 3 with a remainder of 30.
The number 3 becomes the next digit in our result. 
Result so far: 8990.433
Subtracting 270 from 300 leaves us with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

The final outcome is 8990.433, with a leftover of 0.003.