172011 divided by 90 
The aim is to understand the frequency of 90 in 172011.

Advancing to step 1:
When dividing 1 by 90, we get 0 with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 1, we get 1.
Include the next digit (7) from the dividend after 1, then repeat: 17 / 90

On to step 2:
If we divide 17 by 90, we get 0 and a remainder of 17.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 17 and we're left with 17.
Append the next digit (2) from the dividend to 17 and continue with: 172 / 90

On to step 3:
If we divide 172 by 90, we get 1 and a remainder of 82.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Subtract 90 from 172 to get 82.
Include the next digit (0) from the dividend after 82, then repeat: 820 / 90

Moving on to step 4:
90 can be fit into 820 9 times, resulting in a remainder of 10.
Record the quotient 9 as the next digit in the result. 
Result so far: 19.0
Deduct 810 from 820 and we're left with 10.
Fetch the next digit (1) from the dividend, attach it to 10 and continue: 101 / 90

Advancing to step 5:
If we divide 101 by 90, we get 1 and a remainder of 11.
Write down 1 as next digit of the result. 
Result so far: 191.0
If we take 90 away from 101, we end up with 11.
Grab the next digit (1) from the dividend, add it to 11, then carry on: 111 / 90

Let's proceed to step 6:
When dividing 111 by 90, we get 1 with a remainder of 21.
The number 1 becomes the next digit in our result. 
Result so far: 1911.0
If we subtract 90 from 111, we get 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Step 7:
When dividing 210 by 90, we get 2 with a remainder of 30.
Use 2 as the next digit of our solution. 
Result so far: 1911.2
Subtracting 180 from 210 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.

Moving on to step 8:
90 goes into 300 3 times with a remainder of 30.
Use 3 as the next digit of our solution. 
Result so far: 1911.23
Deduct 270 from 300 and we're left 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.

Going ahead to step 9:
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: 1911.233
Subtract 270 from 300 to 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.

After the division, we end up with 1911.233 and a remainder of 0.003.